White spruce has a transcontinental range in North America. In Canada, its contiguous distribution encompasses virtually the whole of the Boreal, Subalpine, Montane, Columbia, Great Lakes–St. Lawrence, and Acadian Forest Regions, extending into every province and territory. On the west coast of Hudson Bay, it extends to Seal River, about 59°N, "from which the northward limit runs apparently almost directly north-west to near the mouth of the Mackenzie River, or about latitude 68°". Collins and Sumner reported finding white spruce within 13 km of the Arctic coast in the Firth Valley, Yukon, at about 69°30′ N, 139°30′ W. It reaches within 100 km of the Pacific Ocean in the Skeena Valley, overlapping with the range of Sitka spruce (Picea sitchensis), and almost reaching the Arctic Ocean at latitude 69° N in the District of Mackenzie, with white spruce up to 15 m high occurring on some of the islands in the Delta near Inuvik. The wide variety of ecological conditions in which 4 Quebec conifers, including white spruce, are able to establish themselves, was noted by Lafond, but white spruce was more exacting than black spruce. In the United States, the range of white spruce extends into Maine, Vermont, New Hampshire, New York, Michigan, Wisconsin, Minnesota, and Alaska, where it reaches the Bering Strait in 66°44′ N" at Norton Bay and the Gulf of Alaska at Cook Inlet.
Southern outliers have been reported in southern Saskatchewan and the Cypress Hills of southwestern Saskatchewan and southeastern Alberta, northwestern Montana, south-central Montana, in the Black Hills on the Wyoming–South Dakota boundary, on the Manitoba–North Dakota boundary, and at Shushan, New York.
White spruce is the northernmost tree species in North America, reaching just north of 69°N latitude in the Mackenzie River delta. It grows between sea level and an elevation of 1,520 m (4,990 ft). Its northern distribution roughly correlates to the location of the tree line, which includes an isothermic value of 10 °C (50 °F) for mean temperature in July, as well as the position of the Arctic front; cumulative summer degree days, mean net radiation, and the amount of light intensities also figure. White spruce is generally found in regions where the growing season exceeds 60 days annually.
The southern edge of the zone in which white spruce forms 60% or more of the total stand corresponds more or less to the July isotherm of 18 °C (64 °F) around the Great Lakes; in the Prairie Provinces its limit is north of this isotherm. During the summer solstice, day length values range from 17 hours at its southern limits to 24 hours above the Arctic Circle.
One of the hardiest conifers, white spruce in parts of its range withstands mean daily January temperature of −6.7 °C (19.9 °F) and extreme minimum temperatures as low as −56.5 °C (−69.7 °F); minimum temperatures of −50 °C (−58 °F) are general throughout much of the range except the southernmost and southeasternmost parts. By itself, or with black spruce and tamarack (Larix laricina), white spruce forms the northern boundary of tree-form growth. White spruce up to 15 m in height occur at 69°N on islands in the Mackenzie Delta near Inuvik in the Northwest Territories. Hustich (1966) depicted Picea spp. as forming the northernmost limit of tree growth in North America.
The arctic or northern timberline in North America forms a broad transition zone from Labrador to northern Alaska. In Labrador, white spruce is not abundant and constitutes less than 5% of the forest, with a range that coincides very closely with that of black spruce but extending slightly further north.
The range of white spruce extends westwards from Newfoundland and Labrador, and along the northern limit of trees to Hudson Bay, Northwest Territories, Yukon, and into northwestern Alaska. Across western Canada and Alaska, white spruce occurs further north than black spruce, and, while poplar (Populus), willow, and birch may occur along streams well into the tundra beyond the limits of spruce, the hardwoods are usually no more than scrub. Spruce characteristically occurs in fingers of tree-form forest, extending far down the northern rivers and as scattered clumps of dwarfed “bush” spruce on intervening lands. In Manitoba, Scoggan noted that the northernmost collection of white spruce was at latitude 59°48’N, but Bryson et al. found white spruce in the northern edge of continuous forest in central Canada at Ennadai Lake, about 60°45′ N, 101°’W, just north of the northwest corner of Manitoba. Bryson et al. noted that the forest retained “the same general characteristics as when it was first described [by Tyrrell] in 1896”. Collins and Sumner reported finding white spruce within 13 km of the Arctic coast in the Firth valley, Yukon, at about 69°30′ N, 139°30′ W, and Sargent noted that white spruce in Alaska “reached Behring Strait in 66°44′ N”.
Climate, especially temperature, is obviously a factor in determining distributions of northern flora. Halliday and Brown suggested that white spruce's northern limit corresponds “very closely” with the July mean monthly isotherm of 10 °C in Ungava, but that the northern limit west of Hudson Bay was south of that isotherm. Other climatic factors that have been suggested as affecting the northern limit of white spruce include: cumulative summer degree days, position of the Arctic front in July, mean net radiation especially during the growing season, and low light intensities. Topography, soil conditions, and glaciation may also be important in controlling northern limits of spruce.
The southern limit of distribution of white spruce is more complex. From east of the main range of coastal mountains in British Columbia, the southern continuous limit of white spruce is the forest/prairie interface through Alberta, Saskatchewan, Manitoba, the northern parts of Minnesota and Wisconsin, central Michigan, northeastern New York, and Maine. Sargent and Harlow and Harrar also included Vermont and New Hampshire; and, while Dame and Brooks excluded New York and states further west, they included Massachusetts as far south as Amherst and Northampton, “probably the southern limit of the species” in that area. Nisbet gave the range of white spruce as extending to “Carolina”, but he did not recognize red spruce as a species and presumably included it with white spruce.
Towards the southern parts of its range, white spruce encounters increasingly effective ecological competition from hardwoods, some of which may reinforce their growth-rate or sprouting competitiveness with allelopathic depredation of coniferous regeneration. Further southward extension of the distribution is inhibited by white spruce's cold requirement.


As an exotic, white spruce is widespread but uncommon. It was introduced into England and parts of continental Europe in or soon after the year 1700, into Denmark about 1790, and into Tasmania and Ceylon shortly before 1932.
Nisbet noted that firmly-rooted white spruce served very well to stabilize windswept edges of woods in Germany. In a narrow belt of mixed Norway and white spruces over an extremely exposed hilltop crest at high elevation in northern England, the Norway spruce were “completely dwarfed” whereas the white spruce had reached heights of between 3 and 4.3 m. The age of the belt was not recorded, but adjoining 66-year-old stands may have been of the same vintage.
White spruce has also been used as a minor plantation species in England and Scotland. In Scotland, at Corrour, Inverness-shire, Sir John Stirling Maxwell in 1907 began using white spruce in his pioneering plantations at high elevations on deep peat. However, plantations in Britain have generally been unsatisfactory, mainly because of damage by spring frosts after mild weather had induced flushing earlier in the season. However, the species is held in high regard in the Belgian peat region, where it grows better than do the other spruces.


White spruce is a climax canopy tree in the boreal forests of Canada and Alaska. It generally occurs on well-drained soils in alluvial and riparian zones, although it also occurs in soils of glacial and lacustrine origin. The understory is dominated by feather mosses (Hylocomium splendens, Pleurozium schreberi, Ptilium crista-castrensis) and fork mosses, and occasionally peat moss. In the far north, the total depth of the moss and underlying humus is normally between 25 to 46 cm (10 to 18 in), although it tends to be shallower when hardwoods are present in the stand.
White spruce grows in soils with pH values of 4.7–7.0, although they have been found in soils as acidic as 4.0 in subalpine fir forests in the Northwest Territories. A presence of calcium in the soil is common to white spruce found in northern New York. White spruce most commonly grows in the soil orders of Alfisols and Inceptisols. Soil properties such as fertility, temperature, and structural stability are partial determinants of the ability of white spruce to grow in the extreme northern latitudes. In the northern limits of its range, white spruce is the climax species along with black spruce; birch and aspen are the early succession species.Wildfires typically occur every 60 to 200 years, although they have been known to occur as infrequently as every 300 years.
White spruce will grow in USDA Growing Zones 3–7, but is not adapted to heat and humidity and will perform poorly in a hot climate. The tree attains its greatest longevity and growth potential in Zones 3–4.


White spruce occurs on a wide variety of soils, including soils of glacial, lacustrine, marine, and alluvial origins; overlying basic dolomites, limestones and acidic Precambrian and Devonian granites and gneisses; and Silurian sedimentary schists, shales, slates, and conglomerates. The wide range of textures accommodated includes clays, even those that are massive when wet and columnar when dry, sand flats, and coarse soils. Its occurrence on some organic soils is not characteristic, except perhaps on shallow mesic organic soils in Saskatchewan and in association with black spruce on organic soils in central Yukon.
Podzolized, brunisolic, luvisolic, gleysolic, and regosolic (immature) soils are typical of those supporting white spruce throughout the range of the species. Soils supporting white spruce are most commonly Alfisols or Inceptisols. In the podzol region of Wisconsin, white spruce occurs on loam podzols, podzolized gley loams, strongly podzolized clays, gley-podzol clays, stream-bottom soils, and wood peat. Moist sandy loams also support good growth. On sandy podzols, it is usually a minor species. Good development occurs on moist alluvium on the banks of streams and borders of swamps. White spruce makes good growth on well-drained lacustrine soils in Alberta Mixedwoods, on moderately-well-drained clay loams in Saskatchewan,, and on melanized loams and clays (with sparse litter and a dark-coloured organically-enriched mineral horizon) in the Algoma district of Ontario.
White spruce becomes less accommodating of soil with increasing severity of climate. The distribution of white spruce in Labrador seems to depend almost entirely on the character of the soil, and between the southwestern shores of Hudson Bay and the northeastern regions of Saskatchewan, white spruce is confined to very local physiographic features, characterized by well-drained or fertile soils.
On dry, deep, outwash deposits in northern Ontario, both white spruce and aspen grow slowly. But, broadly, white spruce is able to tolerate considerable droughtiness of sites that are fertile, and no fertile site is too moist unless soil moisture is stagnant. Soil fertility holds the key not just to white spruce growth but to the distribution of the species. At least moderate fertility is needed for good growth, but white spruce occurs on many sites where nutrient deficiencies depress its growth more than that of black spruce, red spruce, Norway spruce, and the pines generally. Minimum soil-fertility standards recommended for white spruce sufficient to produce 126 to 157 m³/ha of wood at 40 years are much higher than for pine species commonly planted in the Lake States (Wilde 1966): 3.5% organic matter, 12.0 meq/100 g exchange capacity, 0.12% total N, 44.8 kg/ha available P, 145.7 kg/ha available K, 3.00 meq/100 g exchangeable Ca, and 0.70 meq/100 g exchangeable Mg.
Forest floors under stands dominated by white spruce respond in ways that vary with site conditions, including the disturbance history of the site. Composition, biomass, and mineral soil physical and chemical properties are affected. In Alaska, the accumulation of organic layers (to greater thicknesses in mature stands of spruce than those in hardwood stands on similar sites) leads to decreased soil temperatures, in some cases leading to the development of permafrost. Acidity of the mineral soil sampled at an average depth of 17 cm in 13 white spruce stands on abandoned farmland in Ontario increased by 1.2 pH units over a period of 46 years.
A considerable range of soil pH is tolerated by white spruce. Thrifty stands of white spruce in Manitoba have developed on soils of pH 7.6 at only 10 cm below the surface, and pH 8.4 at 43 cm below the surface; rooting depth in those soils was at least 81 cm. An abundant calcium supply is common to most white spruce locations in New York state. Chlorosis was observed in young white spruce in heavily limed nursery soils at about pH 8.3. Wilde gave 4.7 to 6.5 as the approximate optimum range of pH for white spruce in Wisconsin, but optimum growth seems possible at pH levels up to 7.0 and perhaps higher. Alluvium on the floodplains of northern rivers shows pH levels from 5.0 to 8.2. High-lime ecotypes may exist, and in Canada Forest Section B8 the presence of balsam poplar and white spruce on some of the moulded moraines and clays seems to be correlated with the considerable lime content of these materials, while calcareous soils are favourable sites for northern outliers of white spruce.
Mature stands of white spruce in boreal regions often have well-developed moss layers dominated by feather mosses, e.g., Hylocomium splendens, Pleurozium schreberi, Ptlium crista-castrensis, and Dicranum, rather than Sphagnum. The thickness of the moss–organic layer commonly exceeds 25 cm in the far north and may approach twice that figure. The mosses compete for nutrients and have a major influence on soil temperatures in the rooting zone. Permafrost development in parts of Alaska, Yukon, and the Northwest Territories is facilitated by the insulative organic layer (Viereck 1970a, b, Gill 1975, Van Cleve and Yarie 1986).


White spruce is extremely hardy to low temperatures, provided the plant is in a state of winter dormancy. Throughout the greater part of its range, white spruce routinely survives and is undamaged by winter temperatures of −50 °C (−58 °F), and even lower temperatures occur in parts of the range. Boreal Picea are among the few extremely hardy conifers in which the bud primordia are able to survive temperatures down to −70 °C, −94 °F.
Especially important in determining the response of white spruce to low temperatures is the physiological state of the various tissues, notably the degree of "hardening" or dormancy. A natural progression of hardening and dehardening occurs in concert with the seasons. While different tissues vary in ability to tolerate exposure to stressful temperatures, white spruce, as with woody plants in general, has necessarily developed sufficient winter hardiness in its various tissues to enable them to survive the minimum temperatures experienced in the distribution range.
White spruce is subject to severe damage from spring frosts. Newly flushed shoots of white spruce are very sensitive to spring frost. This sensitivity is a major constraint affecting young trees planted without overstorey nurses in boreal climates.


Forest succession in its traditional sense implies two important features that resist direct examination. First, classical definitions generally connote directional changes in species composition and community structure through time, yet the time frame needed for documentation of change far exceeds an average lifespan. The second feature that defies quantitative description is the end point or climax.
Floodplain deposits in the Northwest Territory, Canada, are important in relation to the development of productive forest types with a component of white spruce. The most recently exposed surfaces are occupied by sandbar vegetation or riparian shrub willows and Alnus incana. With increasing elevation, the shrubs give way successively to balsam poplar and white spruce forest. In contrast, older floodplains, with predominantly brown wooded soils, typically carry white spruce–trembling aspen mixedwood forest.
Interrelationships among nutrient cycling, regeneration, and subsequent forest development on floodplains in interior Alaska were addressed by Van Cleve et al., who pointed out that the various stages in primary succession reflect physical, chemical, and biological controls of ecosystem structure and function. Thus, each successional stage has a species combination in harmony with site quality. Short-circuiting succession by planting a late successional species such as white spruce on an early successional surface may result in markedly reduced growth rates because of nitrogen insufficiency. Without application of substantial amounts of fertilizer, use would have to be made of early successional alder and its site-ameliorating additions of nitrogen.
Neiland and Viereck noted that “the slow establishment and growth of spruce under birch stands [in Alaska] may be partially due to effects of shading and general competition for water and nutrients, but may also be more directly related to the birch itself. Heikinheimo found that birch ash inhibited white spruce seedlings, and Gregory found that birch litter has a smothering effect on spruce seedlings.".
On dry upland sites, especially south-facing slopes, the mature vegetation is white spruce, white birch, trembling aspen, or a combination of these species. Succession follows in one of two general patterns. In most cases, aspen and birch develop as a successional stage after fire before reaching the spruce stage. But, occasionally, with optimal site conditions and a source of seed, white spruce will invade with the hardwoods or within a few years thereafter, thereby producing even-aged white spruce stands without an intervening hardwood stage.


The White Spruce Cover Type may include other species in small numbers. In Alaska, associates include paper birch, trembling aspen, balsam poplar, and black spruce; in western Canada, additional associates are subalpine fir, balsam fir, Douglas-fir, jack pine, and lodgepole pine. Seral species giving way to white spruce include paper birch, aspen, balsam poplar, jack pine, and lodgepole pine. On certain river bottom sites, however, black spruce may replace white spruce. Earlier successional stages leading to the white spruce climax are the white spruce–paper birch, white spruce–aspen, balsam poplar, jack pine, and lodgepole pine types. The type shows little variation. The forest is generally closed and the trees well formed, other than those close to the timberline. Lesser vegetation in mature stands is dominated by mosses. Vascular plants are typically few, but shrubs and herbs that occur “with a degree of regularity” include: alder, willows, mountain cranberry, red-fruit bearberry, black crowberry, prickly rose, currant, buffaloberry, blueberry species, bunchberry, twinflower, tall lungwort, northern comandra, horsetail, bluejoint grass, sedge species, as well as ground-dwelling mosses and lichens. Several white spruce communities have been identified in interior Alaska: white spruce/feathermoss; white spruce/dwarf birch/feathermoss; white spruce/dwarf birch/sphagnum; white spruce/avens/moss; and white spruce/alder/bluejoint.
Of the Eastern Forest Cover Types recognized by the Society of American Foresters, only one, White Spruce, names that species in its title. The eastern White Spruce Cover Type, as defined, encompasses white spruce both in pure stands, and in mixed stands "in which white spruce is the major [undefined] component."
In most of its range, white spruce occurs more typically in association with trees of other species than in pure stands.
White spruce is an associated species in the following Eastern Forest cover types, by the Society of American Foresters; in the Boreal Forest Region: (1) jack pine, (5) balsam fir, (12) black spruce, (16) aspen, (18) paper birch, and (38) tamarack; in the Northern Forest Region: (15) red pine, (21) eastern white pine, (24) hemlock-yellow birch, (25) sugar maple-beech-yellow birch, (27) sugar maple, (30) red spruce-yellow birch, (32) red spruce, (33) red spruce-balsam fir, (37) northern white-cedar, and (39) black ash-American elm-red maple.


Outbreaks of spruce beetles have destroyed over 2,300,000 acres (9,300 km²) of forests in Alaska.
Although sometimes described, e.g., by Switzer (1960), as relatively resistant to attack by insects and disease, white spruce is far from immune to depredation. Important insect pests of white spruce include the spruce budworm (Choristoneura fumiferana), the yellow-headed spruce sawfly (Pikonema alaskensis), the European spruce sawfly (Gilpinia hercyniae), the spruce bud moth (Zeiraphera canadensis), and spruce beetle (Dendroctonus rufipennis). As well, other budworms, sawflies, and bark beetles, gall formers, bud midges, leaf miners, aphids, leaf eaters, leaf rollers, loopers, mites, scales, weevils, borers, pitch moths, and spittlebugs cause varying degrees of damage to white spruce.
A number of sawflies feed on spruce trees. Among them European spruce sawfly, yellow-headed spruce sawfly, green-headed spruce sawfly and the spruce webspinning sawfly.
More than a dozen kinds of looper feed on the spruces, fir, and hemlock in eastern Canada. The full-grown larvae of the larvae vary in length from 15 mm to 35 mm. Some feed briefly in the fall and complete their feeding in the spring; others feed mainly in the summer; still others feed mainly in the late summer and fall.
The fall and spring feeding group includes the dash-lined looper (Protoboarmia porcelaria indicataria), the diamond-backed looper (Hypagyrtis piniata), the fringed looper (Campaea perlata), and the false loopers (Syngrapha species). The summer feeding group includes the false hemlock looper (Nepytia canosaria Walker), occasionally occurring in large numbers and usually in conjunction with the hemlock looper (Lambdina fiscellaria), the Eupithecia species, the yellowlined conifer looper (Cladara limitaria), and the saddleback looper (Ectropis crepuscularia).
The late summer and fall group includes the common spruce-fir looper (Semiothisa signaria dispuncta) and the similar hemlock angle (moth) Macaria fissinotata on hemlock, the small spruce loopers Eupithecia species, the gray spruce looper Caripeta divisata, occasionally abundant, the black-dashed hydriomena moth (Hydriomena divisaria), and the whitelined looper (Eufidonia notataria).


Wildlife such as deer, rabbits, and grouse browse the foliage during the winter.
The wood of white spruce is of a lower quality than that of Engelmann spruce, but is stronger. It was used to make shelters and as firewood by Native Americans and European settlers in Alaska, where lodgepole pine does not grow. The wood is of major economic importance in Canada, being harvested for paper and construction. It is also used as a Christmas tree.
The wood is also exported to Japan where, known as "shin-kaya", it is used to make go boards as a substitute for the rare kaya wood.
Black Hills Spruce (Picea glauca var. densata) is used for bonsai.
White spruce is the provincial tree of Manitoba and the state tree of South Dakota.
The new growth or tips of white spruce is used in beer making, gin production, flavouring pop, candy making or in pickles and preserves.


Several geographical varieties have been described, but are not accepted as distinct by all authors. These comprise, from east to west:
Picea glauca var. glauca (typical or eastern white spruce): from Newfoundland west to eastern Alberta, on lowland plains.
Picea glauca var. densata (Black Hills white spruce): The Black Hills in South Dakota.
Picea glauca var. albertiana (Alberta white spruce): The Rocky Mountains in Alberta, British Columbia and northwest Montana.
Picea glauca var. porsildii (Alaska white spruce): Alaska and Yukon.
The two western varieties are distinguished by pubescent shoots, and may be related to extensive hybridisation and intergradation with the closely related Engelmann spruce found further south in the Rocky Mountains. White spruce also hybridises readily with the closely related Sitka spruce where they meet in southern Alaska and northwestern British Columbia; this hybrid is known as Picea × lutzii.


Numerous cultivars of various sizes, colours and shapes have been selected for use in parks and gardens. The following have gained the Royal Horticultural Society's Award of Garden Merit.
Picea glauca ‘Echiniformis’
Picea glauca var. albertiana ‘Alberta Globe’
Picea glauca var. albertiana ‘Conica’
'Conica' is a dwarf conifer with very slender leaves, like those normally found only on one-year-old seedlings, and very slow growth, typically only 2–10 cm (0.79–3.94 in) per year. Older specimens commonly 'revert', developing normal adult foliage and starting to grow much faster; this 'reverted' growth must be pruned if the plant is to be kept dwarf.


P. glauca has three different genomes; a nuclear genome, a mitochondrial genome, and a plastid (i.e. chloroplast) genome. The large (20 Gbp) nuclear genome of P. glauca (genotype WS77111) was published in 2015, and the organellar (plastid and mitochondrial) genomes (genotype PG29) were published in SD Jackman et al. 2015. The plastid genome of P. glauca (genotype WS77111) has also been published.


Picea mariana, the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and Labrador and is that province's most numerous tree. The range of the black spruce extends into northern parts of the United States: in Alaska, the Great Lakes region, and the upper Northeast. It is a frequent part of the biome known as taiga or boreal forest.
The Latin specific epithet mariana means “of the Virgin Mary”.


P. mariana is a slow-growing, small upright evergreen coniferous tree (rarely a shrub), having a straight trunk with little taper, a scruffy habit, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages 5–15 m (15–50 ft) tall with a trunk 15–50 cm (6–20 in) diameter at maturity, though occasional specimens can reach 30 m (98 ft) tall and 60 cm (24 in) diameter. The bark is thin, scaly, and grayish brown. The leaves are needle-like, 6–15 mm (1⁄4–9⁄16 in) long, stiff, four-sided, dark bluish green on the upper sides, paler glaucous green below. The cones are the smallest of all of the spruces, 1.5–4 cm (1⁄2–1+1⁄2 in) long and 1–2 cm (1⁄2–3⁄4 in) broad, spindle-shaped to nearly round, dark purple ripening red-brown, produced in dense clusters in the upper crown, opening at maturity but persisting for several years.
Natural hybridization occurs regularly with the closely related P. rubens (red spruce), and very rarely with P. glauca (white spruce).
It differs from P. glauca in having a dense cover of small hairs on the bark of young branch tips, an often darker reddish-brown bark, shorter needles, smaller and rounder cones, and a preference for wetter lowland areas. Numerous differences in details of its needle and pollen morphology also exist but require careful microscopic examination to detect. From true firs, such as Abies balsamea (balsam fir), it differs in having pendulous cones, persistent woody leaf-bases, and four-angled needles, arranged all round the shoots.
Due to the large difference between heartwood and sapwood moisture content, it is easy to distinguish these two wood characteristics in ultrasound images, which are widely used as a nondestructive technique to assess the internal condition of the tree and avoid useless log breakdown.
Older taxonomic synonyms include A. mariana, P. brevifolia, or P. nigra.


Growth varies with site quality. In swamp and muskeg it shows progressively slower growth rates from the edges toward the centre. The roots are shallow and wide spreading, resulting in susceptibility to windthrow. In the northern part of its range, ice pruned asymmetric black spruce are often seen with diminished foliage on the windward side. Tilted trees colloquially called "drunken trees" are associated with thawing of permafrost.
In the southern portion of its range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Great Lakes region it is most abundant in peat bogs and swamps, also on transitional sites between peatlands and uplands. In these areas it is rare on uplands, except in isolated areas of northern Minnesota and the Upper Peninsula of Michigan.
Most stands are even-aged due to frequent fire intervals in black spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils, and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range; however, some ecologists question whether black spruce forests truly attain climax because fires usually occur at 50 to 150 year intervals, while "stable" conditions may not be attained for several hundred years.
The frequent fire return interval, a natural fire ecology, perpetuates numerous successional communities. Throughout boreal North America, Betula papyrifera (paper birch) and Populus tremuloides (quaking aspen) are successional hardwoods that frequently invade burns in black spruce. Black spruce typically seeds in promptly after fire, and with the continued absence of fire, eventually dominates the hardwoods.
Black spruce is a pioneer that invades the sphagnum mat in filled-lake bogs, though often preceded slightly by Larix laricina (tamarack). Black spruce frequently out-competes shade-intolerant tamarack in the course of bog succession. However, as the peat soil is gradually elevated by the accumulation of organic matter, and the fertility of the site improves, balsam fir and northern white cedar (Thuja occidentalis) eventually replace black spruce and tamarack. On drier sites following fires, black spruce can take over stands of faster growing jack pine (Pinus banksiana) by virtue of its ability to grow in partially shaded conditions which inhibit pine seedlings. But black spruce seedlings are themselves intolerant to the low light and low moisture conditions under mature spruce stands. Balsam fir and northern white cedar, both more understory-tolerant species with deeper taproots, survive and eventually succeed the spruce in the absence of fire.
The spruce budworm, a moth larva, causes defoliation, which kills trees if it occurs several years in a row, though black spruce is less susceptible than white spruce or balsam fir. Trees most at risk are those growing with balsam fir and white spruce.


Numerous cultivars have been selected for use in parks and gardens. The cultivar P. mariana 'Nana' is a dwarf form which has gained the Royal Horticultural Society's Award of Garden Merit.


Black spruce is the provincial tree of Newfoundland and Labrador.
The timber is of low value due to the small size of the trees, but it is an important source of pulpwood and the primary source of it in Canada. Fast-food chopsticks are often made from black spruce.
However, it is increasingly being used for making cross laminated timber by companies such as Nordic Structures, which allows the high strength due to the tight growth rings to be assembled into larger timbers.
Along with red spruce, it has also been used to make spruce gum and beer.


Picea obovata, the Siberian spruce, is a spruce native to Siberia, from the Ural Mountains east to Magadan Oblast, and from the Arctic tree line south to the Altay Mountains in northwestern Mongolia.


It is a medium-sized evergreen tree growing to 15–35 m tall, and with a trunk diameter of up to 1.5 m, and a conical crown with drooping branchlets. The shoots are orange-brown, with variably scattered to dense pubescence. The leaves are needle-like, 1–2 cm long, rhombic in cross-section, shiny green to grayish-green with inconspicuous stomatal lines; the leaves subtending a bud are distinctively angled out at a greater angle than the rest of the leaves (a character shared by only two or three other spruces). The cones are cylindric-conic, 5–10 cm long and 1.5–2 cm broad, green or purple, maturing glossy brown 4–6 months after pollination, and have stiff, smoothly rounded scales.
It is an important timber tree in Russia, the wood being used for general construction and paper making. The leaves are used to make spruce beer.
Siberian spruce cone-scales are used as food by the caterpillars of the tortrix moth Cydia illutana.


Siberian spruce and Norway spruce (Picea abies) have turned out to be extremely similar genetically and might be considered two closely related subspecies of P. abies.
Siberian spruce hybridises extensively with Norway spruce where the two species (or subspecies) meet in northeastern Europe; trees over a broad area from extreme northeast Norway and Sweden, northern Finland east to the Ural Mountains are classified as the hybrid Picea × fennica (Regel) Komarov (or P. abies subsp. ×fennica, if the two taxa are considered subspecies); they differ from typical P. obovata from east of the Urals in having cones with less smoothly rounded, often triangular-pointed, scales.


The blue spruce (Picea pungens), also commonly known as green spruce, white spruce, Colorado spruce, or Colorado blue spruce, is a species of spruce tree. It is native to North America, and is found in USDA growing zones 1 through 7. It is found naturally in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming. It has been widely introduced elsewhere and is used as an ornamental tree in many places far beyond its native range. The blue spruce has blue-green colored needles and is a coniferous tree.


In the wild, Picea pungens grows to about 23 m (75 ft), but when planted in parks and gardens it seldom exceeds 15 m (49 ft) tall by 5 m (16 ft) wide. The tree can grow larger if the tip is cut when it is at least 3 years old. It is a columnar or conical evergreen conifer with densely growing horizontal branches. It has scaly grey bark on the trunk with yellowish-brown branches.
Waxy gray-green leaves, up to 3 cm (1 in) long, are arranged radially on the shoots which curve upwards. The pale brown cones are up to 10 cm (4 in) long. Male cones are found on the entire tree, whereas the female cones are found at the top of the tree. This helps to facilitate cross-pollination.
The specific epithet pungens means "sharply pointed", referring to the leaves.
The blue spruce is the state tree of Colorado.


Picea pungens and its many cultivars are often grown as ornamental trees in gardens and parks. It is also grown for the Christmas tree industry.


The blue spruce is attacked by two species of Adelges, an aphid-like insect that causes galls to form. Nymphs of the pineapple gall adelgid form galls at the base of twigs which resemble miniature pineapples and those of the Cooley's spruce gall adelgid cause cone-shaped galls at the tips of branches. The larva of the spruce budworm eat the buds and growing shoots while the spruce needle miner hollows out the needles and makes them coalesce in a webbed mass. An elongated white scale insect, the pine needle scale feeds on the needles causing fluffy white patches on the twigs and aphids also suck sap from the needles and may cause them to fall and possibly dieback. Mites can also infest the blue spruce, especially in a dry summer, causing yellowing of the oldest needles. Another insect pest is the spruce beetle (Dendroctonus rufipennis) which bores under the bark. It often first attacks trees which have blown over by the wind and when the larvae mature two years afterwards, a major outbreak occurs and vast numbers of beetles attack nearby standing trees.
The blue spruce is susceptible to several needle casting diseases which cause the needles to turn yellow, mottled or brown before they fall off. Various rust diseases also affect the tree causing yellowing of the needles as well as needle fall. Canker caused by Cytospora attacks one of the lower branches first and progressively makes its way higher up the tree. The first symptom is the needles turning reddish-brown and falling off. Meanwhile, patches of white resin appear on the bark and the branch eventually dies.


Blue spruce seedlings are shallow roots that penetrate only 6.4 cm (2.5 inches) of soil during the first year. Although freezing can't damage much in blue spruce, frost will cause seedling loss. Shadows in late spring and early autumn minimize this frost heaving loss. Despite the shallow roots, blue spruce is able to resist strong winds. Five years before transplanting, the total root surface area of 2-meter-high trees was doubled by pruning the roots of blue spruce. It also increases the root concentration in drip irrigation pipeline from 40% to 60%, which is an advantage in landscape greening.


Common cultivars (those marked agm have gained the Royal Horticultural Society's Award of Garden Merit):
'Glauca Globosa' agm – shrub from 3–5 feet (0.91–1.52 m) in height
'Fat Albert' – compact perfect cone to 10 feet (3.0 m) of a silver blue color
'Glauca Jean's Dilly' – shrub from 3–6 feet (0.91–1.83 m) in height
'Glauca Pendula' – drooping branches, spreads to about 8 feet (2.4 m) wide by 4 feet (1.2 m) tall
'Hoopsii' agm
'Koster'
'Baby Blue Eyes'
'Baby Blue'


The Navajo and Keres Native Americans use this tree as a traditional medicinal plant and a ceremonial item, and twigs are given as gifts to bring good fortune. In traditional medicine, an infusion of the needles is used to treat colds and settle the stomach. This liquid is also used externally for rheumatic pains. Early people used their wood for building.


Blue spruce generally exists on gentle uplands and sub irrigated slopes, in well-watered tributary drainage, extending down intermittent streams, and on lower northerly slopes.
Blue spruce always grow naturally in the soils which are in the order Mollisols, and the soil will also be in the orders histosols and inceptisols in a lesser extent.
Blue spruce is considered as a pioneer tree species in moist soil in Utah.


Blue spruce usually grows in cool and humid climatic zones where the annual precipitation mainly occurs in the summer.
Blue spruce is most common in Colorado and the Southwest. The annual average temperature ranges from 3.9 to 6.1 degrees C (39 to 43 degrees F). And ranges from - 3.9 to - 2.8 degrees C (25 to 27 degrees F) in January. In July, the average temperature ranges from 13.9 to 15.0 degrees C (57 to 59 degrees F). The average minimum temperature in January ranges from - 11.1 to 8.9 degrees C (12 to 16 degrees F), and the average maximum temperature in July ranges from 21.1 to 22.2 C (70 to 72 degrees F). There is a frost-free period of about 55 to 60 days from June to August.
Annual mean precipitation generally vary from 460 to 610 mm (18 to 24 in). Winter is the season with the poorest rainfall, the precipitation is usually less than 20 percent of the annual moisture falling from December to March. And fifth percent of the annual precipitation occurs during the growing season of the plants.
Blue spruce is generally considered to grow best with abundant moisture. Nevertheless, this species can withstand drought better than any other spruce. It can withstand extremely low temperatures (-40 degrees C) as well. Furthermore, this species is more resistant to high insolation and frost damage compared to other associated species.


Picea rubens, commonly known as red spruce, is a species of spruce native to eastern North America, ranging from eastern Quebec and Nova Scotia, west to the Adirondack Mountains and south through New England along the Appalachians to western North Carolina. This species is also known as yellow spruce, West Virginia spruce, eastern spruce, and he-balsam.


Red spruce is a perennial, shade-tolerant, late successional coniferous tree that under optimal conditions grows to 18–40 m (59–131 ft) tall with a trunk diameter of about 60 cm (24 in), though exceptional specimens can reach 46 m (151 ft) tall and 100 cm (39 inches) in diameter. It has a narrow conical crown. The leaves are needle-like, yellow-green, 12–15 mm (15⁄32–19⁄32 in) long, four-sided, curved, with a sharp point, and extend from all sides of the twig. The bark is gray-brown on the surface and red-brown on the inside, thin, and scaly. The wood is light, soft, has narrow rings, and has a slight red tinge. The cones are cylindrical, 3–5 cm (1+1⁄4–2 in) long, with a glossy red-brown color and stiff scales. The cones hang down from branches.


Red spruce grows at a slow to moderate rate, lives for 250 to 450+ years, and is very shade-tolerant when young. It is often found in pure stands or forests mixed with eastern white pine, balsam fir, or black spruce. Along with Fraser fir, red spruce is one of two primary tree types in the southern Appalachian spruce-fir forest, a distinct ecosystem found only in the highest elevations of the Southern Appalachian Mountains.  Its habitat is moist but well-drained sandy loam, often at high altitudes. Red spruce can be easily damaged by windthrow and acid rain.
Notable red spruce forests can be seen at Gaudineer Scenic Area, a virgin red spruce forest located in West Virginia, the Canaan Valley, Roaring Plains West Wilderness, Dolly Sods Wilderness, Spruce Mountain and Spruce Knob all also in West Virginia and all sites of former extensive red spruce forest. Some areas of this forest, particularly in Roaring Plains West Wilderness, Dolly Sods Wilderness as well as areas of Spruce Mountain are making a rather substantial recovery.


It is closely related to black spruce, and hybrids between the two are frequent where their ranges meet. Genetic data suggests that the red spruce peripatrically speciated from the black spruce during the Pleistocene due to glaciation.


Red spruce is used for Christmas trees and is an important wood used in making paper pulp. It is also an excellent tonewood, and is used in many higher-end acoustic guitars and violins, as well as musical soundboard. The sap can be used to make spruce gum. Leafy red spruce twigs are boiled with sugar and flavoring to make spruce beer. Also it can be made into spruce pudding. It can also be used as construction lumber and is good for millwork and for crates.
Red spruce is the provincial tree of Nova Scotia.


Like most trees, red spruce is subject to insect parasitism. Their insect enemy is the spruce budworm, although it is a bigger problem for white spruce and balsam fir. Other issues that have been damaging red spruce has been the increase in acid rain and current climate change.
One of the consequences of acid rain deposition is the decrease of soil exchangeable calcium and increase of aluminum.  This is because acid precipitation disrupts cation and nutrition cycling in forest ecosystems. Components of acid rain such as H⁺, NO₃⁻, and SO₄²⁻ limit the uptake of calcium by trees and can increase aluminum availability.
Calcium concentration is important for red spruce for physiological processes such as dark respiration and cold tolerance, as well as disease resistance, signal transduction, membrane and cell wall synthesis and function, and regulation of stomata. Conversely, dissolved aluminum can be toxic or can interfere with root uptake of calcium and other nutrients. At the ecosystem and community levels, Calcium availability is associated with community composition, mature tree growth, and ecosystem productivity. One study testing the effects of added aluminum to soil, found that P. rubens mortality rate increased under these conditions.
During the 1980s, increased acid deposition contributed to a loss of high-elevation red spruce trees, due to leached calcium and decreased freezing tolerance. Additionally, the structure of the spruce needle enhances the capture of water and particles, which has been shown to add to soil acidification, nutrient leaching, and forest decline.
However, more recently, reductions in acid deposition have contributed to red spruce resurgence in some mountain areas in the northeastern United States. This increase in red spruce growth has been associated with an increase in rainfall pH, which reduces bulk acidic deposition. This suggests that policies aiming to reduce atmospheric pollution in this area have been effective, although other species sensitive to soil acidification, such as sugar maple, are still continuing to decline.


The Central Appalachian Spruce Restoration Initiative (CASRI) seeks to unite diverse partners with the goal of restoring historic red spruce ecosystems across the high-elevation landscapes of central Appalachians. The partners that make up this diverse group are Appalachian Mountain Joint Venture, Appalachian Regional Reforestation Initiative, Canaan Valley National Wildlife Refuge, Natural Resources Conservation Service, The Mountain Institute, The Nature Conservancy, Trout Unlimited, U.S. Forest Service Northern Research Station, U.S. Forest Service Monongahela National Forest, West Virginia Division of Natural Resources, West Virginia Division of Forestry, West Virginia Highlands Conservancy, West Virginia State Parks, and West Virginia University.
Prior to the late 1800s, 600,000 hectares (1,500,000 acres) of red spruce were in West Virginia. In the late 1800s and early 1900s, a vast amount of logging began in the state and the number of red spruce dwindled to 12,000 hectares (30,000 acres). Silviculture is being used to help restore the population of the lost red spruce.
Significant efforts have been made to increase the growth of red spruce trees in western North Carolina. Most notably by Molly Tartt on behalf of the Daughters of the American Revolution. Tartt, a resident of Brevard North Carolina, embarked on a mission to find the lost red spruce Pisgah Forest that had been planted by the DAR as a memorial to the lives lost during the American Revolution. The forest, consisting of 50,000 trees was dedicated in 1940 and had until recently been forgotten until Tartt located and identified the forest.


Pickeringia is a monotypic genus of flowering plants in the legume family, Fabaceae. It was recently assigned to the unranked, monophyletic Cladrastis clade. It was named after the naturalist Charles Pickering. Its only species is Pickeringia montana, which is known by the common name chaparral pea. It is endemic to California in the United States, where its distribution extends along the Coast Ranges to the Peninsular Ranges, as well as along the Sierra Nevada foothills. It is also known from Santa Cruz Island.
It is one of very few legumes native to the chaparral habitat. Its nitrogen-fixing ability helps it thrive in rocky, sandy soil. The plant is also well-suited to a landscape of hills, slopes, and recently burned areas; its roots spread quickly and help anchor loose soil, preventing erosion.


The chaparral pea rarely sprouts from seed. More often it sends up new stems from roots growing outward from the mother plant. It forms low, dense, thorny thickets of shiny dark green leaves. In spring and summer the plant blooms in bright magenta flowers. It bears pods containing pealike seeds.
There are two subspecies of chaparral pea:
Pickeringia montana subsp. montana is widespread in California.
Pickeringia montana subsp. tomentosa, sometimes called woolly chaparral pea, is limited to the hills of southern California.


The black-backed woodpecker (Picoides arcticus), also known as the Arctic three-toed woodpecker, is a medium-sized woodpecker (23 cm (9.1 in) long) inhabiting the forests of North America.


The black-backed woodpecker was described and illustrated by the English naturalist William John Swainson in 1832 from a specimen collected near the source of the Athabasca River on the eastern slopes of the Rocky Mountains in Alberta, Canada. He coined the binomial name Picus arcticus. The specific epithet arcticus is the Latin word for "northern" or "arctic". The
black-backed woodpecker is now placed in the genus Picoides was erected by the French naturalist Bernard Germain de Lacépède in 1799. The species is monotypic: no subspecies are recognised.


The plumage of adults is black on the head, back, wings and rump. They are white from the throat to the belly; the flanks are white with black bars. Their tail is black with white outer feathers. There is an element of sexual dimorphism in the plumage, with the adult male possessing a yellow cap. Unlike all other woodpeckers except the related American and Eurasian three-toed woodpeckers, this species has three-toed feet.
Measurements:
Length: 9.1 inches (23 cm)
Weight: 2.1–3.1 oz (60–88 g)
Wingspan: 15.8–16.5 in (40–42 cm)


Their breeding range is boreal forest across Canada, Alaska, the Northwestern United States, as well as northern Wisconsin, the Adirondacks in New York, New England, Minnesota, and Upper Michigan. In particular the species is a burnt-forest specialist, feeding on the outbreaks of wood-boring beetles that feed on recently burnt trees. The most important wood boring beetles taken are in the families Cerambycidae and Buprestidae, along with engraver beetles and the mountain pine beetle. Most food is obtained by pecking, a smaller proportion is obtained by gleaning off branches. Black-backed woodpeckers are generally non-migratory but historically have undertaken intermittent irruptions.
Nest excavation occurs in April and May; a fresh nest is drilled each year into the sapwood of dead trees. Abandoned nests are used by other species of bird to nest in. The female lays three or four eggs, and incubation duties are shared between both parents, although the male alone incubates during the night. Upon hatching the altricial chicks are brooded until the nestling phase. Both parents feed the chicks, which take about 24 days to fledge.


The call note of the black-backed woodpecker is a single, sharp pik, and is lower pitched than the call of the American three-toed woodpecker.


Picromerus bidens, the spiny shieldbug or spiked shieldbug, is a carnivorous species of shield bug in the family Pentatomidae.


This species has a wide distribution in the Palaearctic, from 64°N to North Africa and from the British Isles to China. It has also been introduced, probably more than once, to North America, where it has been recorded from more than 180 sites.


These bugs prefer deciduous and mixed forests, heathland, gardens, chalk downland and damp flower-rich meadows.


Picromerus bidens is a large (12 to 13.5 mm long) and distinctive predatory shieldbug. It shows a thick rostrum directed away from head. Body colour is quite variable, generally light to dark brown or bluish, with red-brown antennae and legs and two unmistakable thorn-like brown projections on the sides of the pronotum (hence the species name bidens, meaning "with two teeth"). Front femurs are armed with a ventral spine distally. The early instar nymphs are commonly reddish, while the final instar nymphs are greyish black, with banded antennae and legs.


Both adults and nymphs of the spiny shieldbugs are predatory, feeding on the larvae of other insects, especially on leaf bugs, beetles, aphids and caterpillars. The choice of the prey depend on the season and availability of food. However both adults and nymphs also suck sap from plants. The female lays eggs on tree trunks and leaves. In the spring the larvae hatch, growing to the adult bugs after five moultings. Nymphs become adults by July or August and adults can be found until November. This species usually overwinters as eggs and less frequently as nymphs.


Pieris canidia, the Indian cabbage white, is a butterfly in the family Pieridae found in India, Nepal and Indochina. Pieris rapae is one of the most closely related species in the Pieridae.


The male is white to pale cream on its upperside. The base of the forewing, the basal portion of the costa, and the base and upper margin of the cell have a scattering of black scales. It is black from the apex to about the middle of the terminal margin. On the latter the black extends for a very short distance triangularly along the veins. There is a round black spot in interspace 3. The hindwing has a subcostal black spot as in Pieris rapae but is generally larger and more conspicuous, and a series of four or five terminal black spots that vary in size at the apices of the veins.
Underside: the forewing is white; cell and costa are lightly irrorated (speckled) with black scales; apex is somewhat broadly tinged with ochraceous yellow. Interspaces 1, 3 and 5 have conspicuous subquadrate black spots; the spot in interspace 1 sometimes extends out of interspace 1. That in interspace 5 is ill-defined. Hindwing: from pale, almost white, to dark ochraceous, thickly irrorated all over (with the exception of a longitudinal streak in the cell, and in the darker specimens similar longitudinal streaks in the interspaces) with black scales; costa above vein 8 are chrome yellow. Antennae are black with minute white specks; the long hairs on the head and thorax are greenish grey; the abdomen is black. Beneath, the head, thorax and abdomen are white.
The female is similar to the male on the underside, but the scattering of black scales is more prominent; the black on the apex and termen of the forewing and the black spots on the termen of the hindwing are broader and more extended inwards; on the forewing there is an additional spot in interspace 1, and both this and the spot in interspace 3 in many specimens are connected by a line of black scales along the veins to the outer black border; also the spot in interspace 1 often extends across vein 1 into the interspace below.
It has a wingspan of 42–60 mm.


It lives in sub-Himalayan India and Pakistan from Chitral, Kashmir to Sikkim and Bhutan, from 2,000 to 11,000 ft (610 to 3,350 m) elevation; the hills of southern India; Assam; Upper Myanmar: the Shan States; extending to China.


Pieris marginalis (margined white) is a butterfly species seen across the coast of Western North America as indicated by data collected by eButterfly.


Pieris marginalis (margined white) is a canopy generalist who feeds on the plant family of Brassiceae. The species is unique as it has been seen near and away from disturbed habitat; indicating an adaptation for habitat generalization.


The green-veined white (Pieris napi) is a butterfly of the family Pieridae.


A circumboreal species widespread across Europe and Asia, including the Indian subcontinent, Japan, the Maghreb and North America. It is found in meadows, hedgerows and woodland glades but not as often in gardens and parks like its close relatives the large and small whites, for which it is often mistaken. Like other "white" butterflies, the sexes differ. The female has two spots on each forewing, the male only one. The veins on the wings of the female are usually more heavily marked. The underside hindwings are pale yellow with the veins highlighted by black scales giving a greenish tint, hence green-veined white. Unlike the large and small whites, it rarely chooses garden cabbages to lay its eggs on, preferring wild crucifers. Males emit a sex pheromone that is perceptible to humans, citral, the basic flavor-imparting component of lemon peel oil.
Some authors consider the mustard white and West Virginia white of North America to be conspecific with P. napi  or consider P. napi to be a superspecies. Despite this, the American butterflies, unlike P. napi, cannot successfully use garlic mustard as a host plant. Females will lay eggs on it, mistaking this non-native species for a compatible native mustard, resulting in the death of the offspring. Classification is also an issue concerning the European dark-veined white.


The eggs are laid singly on a wide range of food plants including hedge mustard (Sisymbrium officinale), garlic mustard (Alliaria petiolata), cuckooflower (Cardamine pratense), water-cress (Rorippa nastutium-aquaticum), charlock (Sinapis arvensis), large bitter-cress (Cardamine amara), wild cabbage (Brassica oleracea), and wild radish (Raphanus raphanistrum), and so it is rarely a pest in gardens or field crops. The caterpillar is green and well camouflaged. When full grown it is green above with black warts, from which arise whitish and blackish hairs. There is a darker line along the back and a yellow line low down on the sides. Underneath the colour is whitish-grey. The spiracular line is dusky but not conspicuous, and the spiracles are blackish surrounded with yellow. There is extensive overlap with other leaf-feeding larvae of large and small whites in some wild populations (e.g. in Morocco). It is often found feeding on the same plant as the orange tip but rarely competes for food because it usually feeds on the leaves whereas the orange tip caterpillar feeds on the flowers and developing seed pods. Like other Pieris species it overwinters as a pupa. This is green in colour, and the raised parts are yellowish and brown. This is the most frequent form, but it varies through yellowish to buff or greyish, and is sometimes without markings.


P. napi is found in damp, grassy places with some shade, forest edges, hedgerows, meadows and wooded river valleys. The later generations widen their habitat use in the search for alternative food plants in drier, but flowery places. In the Mediterranean the insect is also found in scrub around mountain streams or springs and on floodplains with Nasturtium officinale. It is found from sea level to high elevations (2500 m in central Europe, 2600 m in Italy, 3600 m in Morocco).


The generations vary with location, elevation and season. In northern Europe there are two or three generations from April to early September. In warmer areas and in some good years there is a fourth generation. In southern Europe there are three or more partially overlapping generations from March to October.


In the typical  form -forma typica- the forewings are creamy-white, irrorated with black towards the base. There is an apical blackish blotch, sometimes broken into several terminal spots ; and a black spot between 3 and 4 (in male sometimes absent)  In the  female there is a black subdorsal posterior spot, and a dorsal confluent mark. The hindwings are creamy-white, the base black-sprinkled and a black costal spot before the apex (in male sometimes
absent). The underside of the hindwings and underside  apex of the forewings is pale yellow the veins edged with a shading of fine black lines, in  the hindwings more broadly.
The ground colour varies from white to cream, sulphur-yellow, chrome yellow and light hues of buff or brown. The spot markings also vary and may be joined or absent. The vein shading varies in colour and in intensity and the shaded bands may be broad or narrow.
Variants, many named, are described by Röber (Europe), Langham (Ireland) and Anon (Britain)


Recent research has shown that when males mate with a female, they inject methyl salicylate along with their sperm. The smell of this compound repels other males, thus ensuring the first male's paternity of the eggs—a form of chemical mate guarding.
After a female mates, she will display a mate refusal posture that releases methyl salicylate during a subsequent courtship. The release of this anti-aphrodisiac will quickly terminate the courtship. Males are very sensitive to differences in methyl salicylate levels, and will use this sense to influence their mating behaviour. However, a virgin female displaying a very similar posture will release a different chemical that will prolong the courtship ritual. Males are sensitive to these chemical and postural differences, and can discriminate between a receptive virgin female and an unreceptive mated female.
The adult male of this species has a distinctive odour that resembles lemon verbena. This smell is associated with specialized androconial scales on male wings.


In the usually polyandrous P. napi, females who mate multiple times have higher lifetime fecundity, lay larger eggs, and live longer compared to females who mate only once. In most organisms it is the female who contributes the most to the reproduction of offspring as she must invest an egg and then carry the zygote. Males, on the other hand, need only provide a sperm that is of low cost. In P. napi, however, mating is unusually costly to males as the ejaculate matter produced contains not only sperm but accessory substances as well. These substances average 15% of male body mass and are incorporated into female soma and reproductive tissues during the mating process. Therefore, the nuptial gift given by P. napi males qualifies both as paternal investment and mating effort. Despite the presence of nuptial gifts and the known benefits to females and offspring, some females are still monogamous. There are multiple reasons in why other species are monogamous like access to males, low sperm population, and age. Some P. napi are likely monogamous due to variation in egg production between polygamous and monogamous females. Polygamous females rely on male mates in order to increase their reproductive output, but polygamous females that only mate twice may not have as high of reproductive output as monogamous females do. This system is unlike other types of butterflies such as Pararge aegeria, where female reproductive effort is independent of male ejaculate.
The amount of ejaculate of virgin males during mating is larger than that of non-virgin males. Females therefore must mate more frequently with non-virgin males in order to obtain the necessary amount of male-derived nutrition.


In P. napi, the nuptial gift is an example of sexual cooperation towards a common interest of both males and females. The existence of nutrients in the ejaculate is beneficial to the females because it increases female fecundity and longevity, and eventually promotes re-mating. The existence of the anti-aphrodisiac, methyl salicylate, is effective in reducing female harassment by other males.
However, the transfer of this ejaculate can cause a conflict over re-mating due to sperm competition. After a female mates, infertile sperm ejaculated by the male will fill the female's sperm storage organ and prevent her from mating. The amount of infertile sperm stored is correlated with the refractory period of a female after mating. Infertile sperm makes up 90% of the sperm count, showing that males manipulate females by preventing them from mating with another male for a certain period of time. Although polyandry benefits females of P. napi by maximizing the amount of transferred nutrients from the male, the infertile sperm storage prolongs female re-mating.
This refractory period makes it harder for females to mate, and females will continue to have difficulty as their age and mating frequency increase. Males who have recently copulated will not transfer as many nutrients to their next mate, but will spend a longer duration of time for each mating. This increases the mating costs for females because they are spending more time copulating and receiving fewer nutrients from the ejaculate. Males take advantage of this because females do not reduce their mating costs by copulating with virgin males. In addition, males will transfer the most methyl salicylate to their first mate to ensure its paternity. However, a female who mates with a virgin male will have the most difficulty re-mating, therefore delaying her from engaging in the preferred polyandry. Males tailor their ejaculate in the sense that the first ejaculate is meant to prolong the refractory period of the female, and every subsequent ejaculate is meant to maximize efficiency in sperm competition.


Fecundity in P. napi varies with the number of eggs produced as well as the lifespan of the female, and is positively influenced by body mass, other genetic factors independent of body size, and with the degree of polyandry. Fecundity increases with the amount of spermatophore material and ejaculate received from males during mating. In particular, mating with recently unmated males can increase overall female reproductive output, though small females are unable to compensate for the negative effects of size on fecundity by mating multiply. However, by mating multiply, polyandrous females have overall higher lifetime fecundity, produce more offspring, and have faster-developing offspring compared to monandrous females.


Despite the benefits of mating multiply, many female P. napi only mate once, irrespective of the number of high quality, more fit, mates available. Monandry is more common in northern populations of P. napi, and sperm competition is correspondingly lower in the north. This polymorphic mating system is partially determined by genetic variability within the females genomes. Monandrous and polyandrous females exhibit different heritable reproductive tactics with monandrous females relying on larval derived resources to realize their fecundity and polyandrous females relying on male donations. When genetically polyandrous females are forced into monandry, due to suboptimal mating conditions, they experience reduced life spans. Monandrous and polyandrous females exhibit different life history strategies: at the start of reproduction females that are monandrous produce more eggs than polyandrous females. It is hypothesized that this life history difference is why monandry is more common in the most northern parts of the species’ range, as early investment in reproduction can be more beneficial with shorter mating seasons.


The maintenance of the two mating systems had been hypothesized to be due to the availability of male nutrients, which can vary within the male-biased operational sex ratio. The male biased sex-ratio can lead to strong competition for mates among the males as well as the males are unlikely to encounter more than one female during the mating season. As a result, females often encounter males that have not recently mated that provide large nuptial gifts. Given the size of the nuptial gift provided by males, means that polyandrous females can substantially increase their lifetime fecundity. However, higher mating rates in females comes with a cost, which can explain the presence of monandrous females in primarily polyandrous populations. Polyandrous females have a higher cost of mating characterized by an increase in time spent looking for mates and time spent mating. This results in a decreased time spent looking for food.


Some authorities consider P. napi to be a superspecies that includes the American species mustard white and West Virginia white as well as the European dark-veined white.
However, the American butterflies cannot successfully reproduce by laying eggs on the invasive weed garlic mustard, Alliaria petiolata, a fact that threatens their survival as garlic mustard out-competes native mustard plants due to having no biological control species present in North America. In Europe, where garlic mustard is native, 76 things consume it.


Pieris napi napi
Pieris napi adalwinda (Fruhstorfer, 1909) Finland, Sweden
Pieris napi meridionalis Heyne & Rühl, 1895 Spain, Italy
Pieris napi segonzaci (le Cerf, 1923) High Atlas
Pieris napi maura (Verity, 1911) Glacières de Blida, Algeria
Pieris napi atlantis (Oberthür, 1923) Azrou, Middle Atlas, Morocco
Pieris napi flavescens (Wagner, 1903) Mödling, Austria
Pieris napi lusitanica Lep. Portug. Porto: 2, 1929 De Sousa Portugal
For others see Wikispecies.


Pieris adalwinda Fruhstorfer, 1909
Pieris arctica Verity, 1911
Pieris canidiaformis Drenowsky, 1910
Pieris dubiosa Röber, 1907
Pieris flavescens Wagner, 1903
Pieris meridionalis Heyne, 1895


Pieris oleracea, or more commonly known as the mustard white, is a butterfly in the family Pieridae native to a large part of Canada and the northeastern United States. The nearly all-white butterfly is often found in wooded areas or open plains. There are two seasonal forms, which make it distinct from other similar species.  Because of climate change, populations are moving further north.
As indicated by the common name, P. oleracea adults and larvae primarily feed on plants in the mustard family, Brassicaceae. The species is threatened by the rapid, and monoculture-forming, spread of the invasive species Alliaria petiolata, which is toxic to larvae. Populations of P. oleracea have been declining. It may be that this butterfly is slowly adapting to garlic mustard. However, it may not be a fast enough process to ensure its survival, due to the high level of aggression on the part of the plant and the continuing encroachment of human development.
Its specific name oleracea means "related to vegetables/herbs" in Latin and is a form of holeraceus (oleraceus).


Pieris oleracea larvae are yellow and shaped like cones, with vertical ridges. Larvae that are mature have many black spots with a green body, dark dorsal stripe, and short, dense hairs. The pupae can range in color from brown to white to green, and have dorsal and apical projections.


There are two seasonal forms of the butterfly, one for spring and one for summer. Above the wings, the butterfly is entirely white, which a small patch of black scales at the tips of the wings. A feature that differentiates this species from other similar species is the green or yellow markings on the underside of the hind wings that run along the veins. In the spring, the green markings are very apparent, and can be seen from the top side of the wing. In the summer, the wing appears almost entirely white, as the markings on the underside of the wing and the black tips are fainter.


This species is mainly found throughout Canada and parts of the northeastern United States. They are often found with other very similar species in specific areas. Their range stretches across Canada starting from Newfoundland to Alberta and other Northwestern Territories. However, they are only found in the foothill regions of Alberta. In British Columbia, populations are found in north and central regions. In Nunavut, they are specifically found near the coast at Coppermine and Arviat. In the Cypress Hills of Saskatchewan, there is a single population that has been found. As for the United States, they are found in the New England states and Great Lakes area.


These butterflies are found in prairies, near streams, and in moist deciduous areas. In the spring, they are found more readily in the moist areas, either the woodlands or open fields.
Pieris oleracea is a biovoltine species, meaning it tends to have two broods seasonally. The time in which they fly can depend on the area the inhabit. Usually, the butterflies migrate once in June, and once again in late July. However, in southern Ontario, there can be three to four generations, and farther up north it has been observed where there is only one generation.


Because of changing climate conditions, broods are expanding farther north.
There has been a steady decline in the populations of P. oleracea, which is being attributed to either climate change, the expansion of the toxic garlic mustard plant, human development, or, most likely, a combination of these factors.
During the day, males observe the population to look for females to mate with.


The larvae feed on various types of Brassicaceae, which can also be referred to as mustard plants. The most common of these types are Cardamines and Boechera, sometimes commonly known as bittercress and rockcress respectively.  Adult butterflies will eat the nectar from these same plants.
There are certain mustard plants that are toxic to the butterflies. Alliaria petiolata, more commonly known as garlic mustard, is an example. Because this species is closely related to host mustards of P. oleracea, it is very similar to their commonly eaten plants, so these butterflies often feed on the toxic species. The native hosts of P. oleracea contain glucosinolates that are similar to those found in A. petiolate, which is why females are attracted to them. However, this specific species is toxic to larvae and causes death. Previous studies have shown that specifically in 1st and 4th instar larvae, several chemicals in A. petiolata reduce chances of survival because the larvae end up consuming less.
Some recent, short-term studies have shown that P. oleracea may be beginning to evolve to use A. petiolata as a host plant.  A. petiolate is an extremely invasive species in much of the United States and is becoming increasingly common in areas with P. oleracea populations. The slow nature of this potential evolution (preliminarily estimated to be as high as 100 generations for it to possibly be occurring), coupled with the dominance of Alliaria petiolata as an invasive species, where it often creates dense herb layer monocultures on the forest floor, at forest edges, along streams, and in other habitats — and the smallness of the populations of P. oleracea, make passively waiting for this adaption to save the species questionable, particularly in light of the repeated blockage of biological control weevil species by the USDA's TAG group, despite multiple petitions from scientists for approval of even the monophagous weevil C. scrobicollis. Researchers have said that the univoltine nature of Pieris virginiensis, coupled with its rarity, makes A. petiolata potentially an even greater threat to its survival, due to a reduced ability to adapt.


The existence of the toxic A. petiolata is detrimental to the species, introduced into the United States in the 19th century. It is unclear to what degree it will remain a threat to the survival of this butterfly over time, due to potential adaption. This species of mustard plant contains the oviposition stimulant sinigrin. Females of this species react very strongly to sinigrin, especially when compared to similar species like P. rapae and P. virginiensis. In similar Pieridae species, sinigrin was found to negatively impact larval survival by affecting a pathway that transforms harmful substances into harmless ones.
With the increasing abundance of A. petiolata, there is concern about the potential adaption rate to what appears to be an incompatible, yet attractive to females, host plant. Studies were done in areas with and without garlic mustard, looking at female selection and larval survival success. One group of females were in an area where garlic mustard was widely established, and the other group was in an area where it was just recently introduced. Despite the fact that garlic mustard is non-native, females in the group with widespread garlic mustard showed an oviposition preference for it. The larvae in this group on the mustard plants had reduced survival rates than those on their normal native hosts. Females in the group with the newly introduced garlic mustard had a wide range in their selection of host plants, and the larval survival rates were also higher in general. Garlic mustard, however, creates monocultures due to its extreme success as an invasive species in the United States, where it lacks over seventy predators that occur in its native areas. This reduces food plant choice by pushing out the native mustards. When comparing the success rates of larvae on the garlic mustard between the two groups, the first group had higher survival success rates than the group with the newly introduced garlic mustard. The increasing selection of using A. petiolata may show an attempt by P. oleracea to adapt to this invasive species but the adaption may be too slow to compensate for the monoculture formation of the plant and the reduction of its host plants from human encroachment such as land development.


Another potential enemy of P. oleracea is a member of its own genus, Pieris rapae. After introduction of this species in an area in New England populated by P. oleracea, the native populations were entirely wiped out. In many cases this appears to be because of competition for foraging sites. However, there has been a case observed where the two species were able to coexist successfully.


DNA barcode data of Pieris oleracea is available through the BOLD systems database and GenBank. The sequence cytochrome oxidase subunit 1 region, the typical region for DNA barcoding, was used and the FASTA file is available.


A specific case of sympatry between P. oleracea and P. rapae was seen in Vermont. Even though the populations had approximately the same territory, each species was able to find a specific niche in the food source or habitat that the other could not use. P. oleracea larvae primarily used Dentaria diphylla during the spring, whereas P. rapae used Barbaea vulgaris in the spring. As for mating, there was no observed interference between the two species. Even though adults were in the same areas, there was no conflict.


Pieris napi – green-veined white
Pieris virginiensis – West Virginia white
Pieris marginalis – margined white


Pilea microphylla can be propagated by dividing the root ball, or taking herbaceous cuttings and rooting them with rooting hormone.  The plant enjoys a thorough watering after the soil has been allowed to dry, and misting has been shown to be beneficial. Direct sunlight causes the leaves to turn brown and fall off, so it prefers filtered light.


Pilea microphylla has been introduced to various tropical and subptropical regions around the world. It is considered an invasive species in Australia, China, Diego Garcia, the Galapagos Islands, the Federated States of Micronesia, Fiji, French Polynesia, Guam, Hawaii, India, Indonesia, Japan, Kiribati, Marshall islands, Nauru, New Caledonia, Niue, Palau, Papua New Guinea, the Philippines, Pitcairn Islands, Singapore,  the Solomon Islands, Tonga, and Wallis and Futuna.


Pilea microphylla var. trianthemoides is a synonym of Pilea trianthemoides


Pilea pumila is an erect annual, growing 0.7 to 70 cm tall. The foliage is opposite, simple with dentate margins, wrinkly (with depressed veins), ovate, and with long petioles. Both the leaves and stems are translucent and bright green, turning bright yellow in autumn. The flowers are small, borne in axillary cymes, unisexual with both genders occurring on the same plant, greenish yellow, and pollinated by wind. Flowers bloom from midsummer through early autumn. Fruits (achenes) are green with purple markings. Roots are fibrous, shallow, and adventitious off the stem in moist areas or when in contact with the soil.
The plant is often mistaken for stinging nettle (Urtica dioica), but can be distinguished by the lack of trichomes, or stinging hairs, and the lower amount of branching of the inflorescences.


Three varieties of Pilea pumila are currently recognized. They are:
P. pumila var. hamaoi - Found in China, Japan, and Korea
P. pumila var. obtusifolia - Restricted to China
P. pumila var. pumila - Widespread in North America and eastern Asia
Among the typical widespread variety pumila, minor differences do exist between the Asian and North American populations. Further taxonomic studies are needed to clarify what level of rank (if any) these differences warrant.


Canadian clearweed is edible, but unpalatable. The plant can be used in classroom demonstrations of transpiration using food coloring due to its translucent stem. It was reportedly used medicinally by certain Native Americans for sinus issues, itch relief and to reduce hunger, and it is sometimes used as a diuretic in Asia.


The plant is host to various caterpillars, including the leaf-mining larvae of Cosmopterix pulchrimella, as well as the aphid Pseudasiphonaphis corni and leafhopper Empoasca recurvata.


Pilosella aurantiaca (fox-and-cubs, orange hawk bit, devil's paintbrush, grim-the-collier) is a perennial flowering plant in the family Asteraceae that is native to alpine regions of central and southern Europe, where it is protected in several regions.


It is a low-growing plant with shallow fibrous roots and a basal rosette of elliptical to lanceolate leaves 5–20 centimetres (2.0–7.9 in) long and 1–3 centimetres (0.39–1.18 in) broad. All parts of the plant exude a milky juice. The flowering stem is usually leafless or with just one or two small leaves. The stem and leaves are covered with short stiff hairs (trichomes), usually blackish in color. The stems may reach a height of 60 centimetres (24 in) and have 2–25 capitula (flowerheads), each 1–2+1⁄2 cm diameter, bundled together at the end of short pedicels. The flowers are orange, almost red, which is virtually invisible to bees, yet they also reflect ultraviolet light, increasing their conspicuousness to pollinators. The flowers are visited by various insects, including many species of bees, butterflies, pollinating flies. The flowers themselves come in a range of colors from a deep rust-orange to a pure yellow and often show striking gradients of color. In the UK, it flowers in June and July.
After flowering, it produces seedpods with a pappus of white or pale brown hairs.
The plant propagates through its wind-dispersed seeds, and also vegetatively by dividing the stolons and shallow rhizomes. in autumn or spring.


The Latin specific epithet aurantiaca means ”orange”, referring to the usual colour of the blooms.
The common name of fox-and-cubs is due to the appearance of the open flowers (the fox) beside the flower buds (the cubs).


P. aurantiaca is widely grown as an ornamental plant in gardens for its very decorative flowers. It is often used in wildflower gardens because its bright orange flowers are highly attractive to a wide array of pollinators.


Orange hawkweed is currently the only hawkweed considered regionally invasive in areas of British Columbia, Canada. It is considered invasive in the East Kootenay, Central Kootenay, Columbia-Shuswap, Thompson-Nicola, Bulkley Nechako, and Cariboo Regional Districts. Invasive hawkweed can replace native vegetation in open, undisturbed natural areas such as meadows, reducing forage and threatening biodiversity. In Victoria and NSW, Australia, hawkweed species are declared as "State Prohibited Weeds" and are controlled under The Bio Security Act 2015. Orange hawkweed is also considered an invasive species in some states in the United States of America, such as Wisconsin and Minnesota. Currently there are several eradication programs operating (often employing volunteers) to locate, prevent the spread of and eradicate any Pilosella or Hieracium plants.


Pilosella caespitosa (synonym Hieracium caespitosum, commonly known as meadow hawkweed, yellow hawkweed,field hawkweed, king devil, yellow paintbrush, devil's paintbrush, yellow devil, yellow fox-and-cubs, and yellow king-devil)
is like several other Pilosella species and has a similar appearance to many of the hawkweeds.


Pilosella caespitosa is a creeping perennial,
with shallow, fibrous roots
and long rhizomes.
The leaves, hairy on both sides (unlike Pilosella floribunda, which looks similar but has hair only on the underside), are up to 6 inches (15 centimeters) long, spathulate, and almost exclusively basal with the exception of 1 or 2 very small cauline leaves. The leaves lie flat to the ground, overlap, and will smother non-vigorous turf.
The stems are bristly and usually leafless, although occasionally a small leaf appears near the midpoint.
Stems, leaves, and bracts have dense, blackish hairs
and exude milky juice when broken.
The 1/2 inch (1 centimeter) flower heads appear in tight clusters at the top
of the 1 to 3 foot (1/3 to 1 meter) stems with 5 to 40 flowers per cluster.Corollas are all ligulate and bright yellow.
Each single flower head is an inflorescence and each petal forms its own seed, making them each a separate flower or
floret.
The seeds are shiny, black, and plumed.
After maturing they are dispersed by wind, clothing, hair, feathers, and some vehicles that disturb fields or soils. P. caespitosa persists and regrows each year from rhizomes and often spreads by stolons,
which can be extensive, creating a dense mat of hawkweed plants (a colony) that practically eliminates other vegetation.
Pilosella caespitosa prefers silt loam, well-drained soil: coarse textures, moderately low in organic matter, and moist. Its presence can be an indicator of low soil fertility or slightly acidic soils.
Pilosella caespitosa has, in the past, been used for healing eyesight. Pliny the Elder had recorded information regarding how other species, specifically hawks, utilized P. caespitosa, specifically believing that they would eat it in an effort to improve eyesight.


Tolerant of drought and trampling, this species finds its habitat where the soil has been neglected. Places like roadsides, neglected residential and commercial landscapes, minimally maintained public parks and open spaces, vacant lots, rubble dump sites, and abandoned grasslands (meadows).
Pilosella caespitosa is an introduced species in North America and can be found in Canada (British Columbia, Manitoba, New Brunswick, Newfoundland, Labrador, Nova Scotia, Ontario, Prince Edward Island, and Quebec)
and the United States (Connecticut, Washington D.C., Georgia, Idaho, Illinois, Indiana, Massachusetts, Maine, Michigan, Minnesota, Montana, North Carolina, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Tennessee, Virginia, Vermont, Washington, Wisconsin, West Virginia, and Wyoming). It is considered a noxious weed in Idaho, Montana, Oregon and Washington.
Pilosella caespitosa's native range includes a large portion of Europe, including Austria, Belarus, Bulgaria, Czechoslovakia, Estonia,  France, Finland, Germany, Greece, Hungary, Latvia, Lithuania, Norway, Poland, Romania, Sweden, Switzerland, Ukraine, and Former Yugoslavia.


Pilosella officinarum (synonym Hieracium pilosella), known as mouse-ear hawkweed, is a yellow-flowered species of flowering plant in the daisy family Asteraceae, native to Europe and northern Asia. It produces single, lemon-coloured inflorescences. Like most hawkweed species, it is highly variable and is a member of a species complex of several dozens of subspecies and hundreds of varieties and forms. It is an allelopathic plant.


It is a hispid (hairy) perennial plant, with a basal rosette of leaves. The whole plant, with the exception of the flower parts, is covered in glandular hairs, usually whitish, sometimes reddish on the stem. The rosette leaves are entire, acute to blunt, and range from 1–12 centimetres (0.39–4.72 in) long and 0.5–2 centimetres (0.20–0.79 in) broad. Their underside is tomentose (covered with hair). The flowering stem (scape) is generally between 5–50 centimetres (2.0–19.7 in) tall, and sprouts from the centre of the basal rosette. The flowerheads are borne singly on the scape and are a pale lemon-yellow colour, with the outermost ligules having a reddish underside. It flowers from May until August and the flowers are visited by various groups of insects, especially flies.
The plant favours dry, sunny areas. It grows well on sandy and similarly less fertile ground types. It produces stolons which generate a new rosette at their extremity, each rosette has the possibility of developing into a new clone forming dense mats in open space. It also propagates by seeds.


It is a known allelopathic plant, whose roots secrete several substances inhibiting root growth, including its own. It can be controlled through rotation with clover and grasses where possible.
Recent research claims that Pilosella officinarum exhibits an atavism by the reemergence of sexual reproduction.


Shetland mouse-ear hawkweed (Pilosella flagellaris subsp. bicapitata) is similar, but has two flowers per leaf stalk.  It is found in the  Shetland Islands only, on rocky coastal grassland. It flowers from May to August.


Mouse-ear hawkweed has become a common introduced invasive species in North America (where it is found in southern Canada and both north-east and north-west United States), and New Zealand. It is a level C noxious weed in the United States (with higher levels in the states of Washington and Oregon), and a weed in Quebec. It does not have special designations in other locations of Canada. It is known to be strongly invasive in New Zealand's tussock fields, where there are no native species of hawkweed, and biological control measures are being undertaken to control it and other similar species. In Victoria and NSW, Australia, Hawkweed Sp. are declared as State Prohibited Weeds and are controlled under The Bio Security Act 2015. Currently there are several eradication programs operating (often employing volunteers) to locate, prevent the spread of and eradicate any Pilosella (Hieracium) sp. plants.
Joseph Pitton de Tournefort mentions that blades covered in this plant's juices were believed to cut through stone as easily as through wood.


The mouse-ear hawkweed contains umbelliferone, a compound similar to coumarin. The plant produces triterpenoids, mainly taraxasterol, but also the 4,4-dimethyl phytosterols alpha- and beta-amyrin, taraxerol, and fern-7en-3beta-ol.


Pinguicula alpina, also known as the alpine butterwort, is a species of carnivorous plant native to high latitudes and altitudes throughout Eurasia.  It is one of the most widespread Pinguicula species, being found in mountainous regions from Iceland to the Himalayas. Native to cold climates, it is a temperate species, forming prostrate rosettes of green to red leaves and white flowers in the summer and a tight hibernaculum during a period of winter dormancy in the winter.  Like all members of the genus, P. alpina uses mucilaginous glands covering the surface of its summer leaves to attract, trap, and digest arthropod prey.


Pinguicula alpina is a small perennial herb, reaching a height of 5–15 cm (2-6 in.) when in flower. The plant is supported by 1–2 cm (0.4-0.8 in) long roots, which are fleshy, yellow-white and branching. P. alpina is the only temperate Pinguicula which retains these roots year-round; the roots of other temperate species wither with the winter dormancy. This allows it to invest more of its income (nutrients derived from prey) into long-term storage, compared to other subarctic Pinguicula which are income breeders and invest these nutrients into immediate plant size and flowering increases.


The five to eight fleshy, light-green to reddish, elliptic to lanceolate leaves form a ground-hugging rosette up to 6 cm (2.5 in) in diameter. The upper surface of the leaves are sticky from the mucilage secreted by stalked glands covering the leaf surface. Small insects alighting upon this surface are caught by the mucilage, upon which sessile glands embedded in the leaf surface (except for the central vein) secrete digestive enzymes to digest the prey. The leaves of this species are able to further aid digestion by growing such that the leaf edge rolls toward the center, bringing additional glands into contact with the prey. Most plants are reddish-green in full sun, though some plant will turn completely red while a smaller percentage will remain completely green.


Pinguicula alpina only begins flowering after several years of growth. Six to eight (occasionally up to 13) flowers are borne singly on unbranched inflorescences up to 12 cm (5 in) tall. The zygomorphic flowers are 10–16 mm (⅜-⅝ in) long with a short yellow-green spur and are composed of a two-lobed upper lip and three-lobed lower lip. They are white with one or sometimes three yellow markings on the lower lip. These can be variable in size and shape. The flowers are protogynous, meaning that the female stigmas mature before the male anthers, and are pollinated by flies.
Fertilized flowers mature into 6–9 mm (¼-⅜ in) by 2–3 mm (1/16-⅛ in) seed capsules bearing copious numbers of tiny, rust-brown seeds.


Healthy plants produce 3 mm (⅛ in) bulblets at the leaf axils following the flowering period. These form new plants the following year, serving as a means of vegetative reproduction. Plants in arctic habitats do not form these bulblets.


Pinguicula alpina is hemicryptophytic, in that the plant survives the cold winter conditions by reducing to a bud resting on the soil surface. This bud, called a hibernaculum, is composed of small, densely packed leaves, which unfurl with the coming of spring. Although most hibernacula in this genus lose their roots during this period, P. alpina is unique in that it retains them.


Pinguicula alpina is found in high altitudes and latitudes throughout Europe and Asia, with the densest populations concentrated in the Alps and northern Scandinavia. Around the last ice age the plant was distributed throughout Asia, where it still remains today in Siberia, Mongolia, and the Himalayas. P. alpina is one of the most widely distributed members of the genus Pinguicula.
In 2012, a population of more than 1000 P. alpina individuals was discovered in Ringhorndalen, Svalbard. Previously unknown to exist in the archipelago, it now marks the northernmost population of the species.


This species grows from sea level in northwest Siberia to altitudes of up to 4,100 m (13,500 ft), in open, sunny locations. The plant prefers wet soils such as seeps with alkali to neutral pH. P. alpina is, however, unusually tolerant of soil dryness for a temperate butterwort. It is typically found in subalpine seeps or bogs or alpine rock-meadows.
In alpine locations P. alpina is often found growing with Carex firma (an alpine grass), Bistorta officinalis, Dryas octopetala, and Pedicularis rostratocapitata. Here it most often grows in a Caricetum firmae plant association, part of the Seslerion albicantis (alpine bluegrass) plant community.
In montane locations it is most often associated with Caricion davallianae and Cratoneurion commutati plant communities, growing together with Schoenus nigricans, Schoenus ferrugineus, Epipactis palustris, Cochlearia officinalis and Pinguicula vulgaris.


Due to its widespread distribution, P. alpina enjoys a relatively secure future. In some regions in Europe, however, it is uncommon enough to be threatened by development or agriculture. The species, for example, used to be found in northern Scotland, but has since been eradicated there and is no longer found growing natively on the British Isles. The species is protected in Germany by the "Bundesartenschutzverordnung", and is also protected locally in some Swiss cantons and the Pannonian and Alpine foothill regions of Austria.


European folk medicine didn't distinguish between various butterwort species, but prescribed them for sores, swelling, sciatica, and liver disease, as well as stomach aches, chest pain and respiratory problems. Its supposed effectiveness against these ailments is attributed to the cinnamic acid found in the plants.


In 1583, Clusius distinguished between two butterwort forms in his Historia stirpium rariorum per Pannoniam, Austriam: a blue-flowered form (P. vulgaris) and a white-flowered form (P. alpina), which Linnaeus included in his Species Plantarum in 1753 along with P. villosa and P. lusitanica.
Since that time countless subgenera, varieties and forms have been described in an attempt to reassign or further delimitate the species. These, however, have not gained wide acceptance.
With the exception of the extremely rare P. crystallina, P. alpina is the only European species which is not a member of the section Pinguicula, belonging instead to the section Micranthus, of which it the type species. The other three species of this section are native to northern Russia, Siberia and Japan.
Although it is not closely related, P. alpina forms natural hybrids with P. vulgaris, forming the hybrid Pinguicula × hybrida.


Linnee, in Spec. pl. ed. 1 (1753) 17
Thorén, L. Magnus and Karlsson, P. Staffan (1998). Effects of supplementary feeding on growth and reproduction of three carnivorous plant species in a subarctic environment. Journal of Ecology; Jun98, Vol. 86 Issue 3, p501-510
Patrat, Eric, 1998; Pinguicula alpina (trip report)
"New, carnivorous plant species found in Svalbard". UNIS. 2013-10-03. Retrieved 2019-06-04.


Jack pine (Pinus banksiana) is an eastern North American pine. Its native range in Canada is east of the Rocky Mountains from the Mackenzie River in the Northwest Territories to Cape Breton Island in Nova Scotia, and the north-central and northeast of the United States from Minnesota to Maine, with the southernmost part of the range just into northwest Indiana and northwest Pennsylvania. It is also known as grey pine and scrub pine.
In the far west of its range, Pinus banksiana hybridizes readily with the closely related lodgepole pine (Pinus contorta). The species epithet banksiana is after the English botanist Sir Joseph Banks.


Pinus banksiana ranges from 9–22 m (30–72 ft) in height. Some jack pines are shrub-sized, due to poor growing conditions. They do not usually grow perfectly straight, resulting in an irregular shape similar to pitch pine (Pinus rigida). This pine often forms pure stands on sandy or rocky soil. It is fire-adapted to stand-replacing fires, with the cones remaining closed for many years, until a forest fire kills the mature trees and opens the cones, reseeding the burnt ground.
Its leaves are needle-shaped, evergreen, in fascicles of two, needle-like, straight or slightly twisted, stiff, sharp-pointed, light yellowish-green, spread apart; edges toothed and 2–4 cm (3⁄4–1+1⁄2 in) long. The bundle-sheath is persistent. The buds are blunt pointed, up to 15 mm long, reddish-brown, and resinous. On vigorous shoots, there is more than one cyclic component (two or more rings in the molecular structure). The bark is thin, reddish-brown to gray in color in juvenile stages. As the tree matures it becomes dark brown and flaky. The wood is moderately hard and heavy, weak, light brown colour. The seed cones vary in shape, being rectanglar to oval, cone shaped, straight or curved inward. The cones are 3–5 cm (1+1⁄4–2 in) long, the scales with a small, fragile prickle that usually wears off before maturity, leaving the cones smooth.

Unusually for a pine, the cones normally point forward along the branch, sometimes curling around it. That is an easy way to tell it apart from the similar lodgepole pine in more western areas of North America. The cones on mature trees are serotinous. They open when exposed to intense heat, greater than or equal to 50 °C (122 °F). The typical case is in a fire, however cones on the lower branches can open when temperatures reach 27 °C (81 °F) due to the heat being reflected off the ground. Additionally, when temperatures reach −46 °C (−51 °F), the cones will open, due to the nature of the resin.