Overstory #246 - Introduction to temperate homegardens
Humans have cultivated plants in a number of different arrangements for thousands of years, including mimicking forest growth to create agricultural systems that can be categorized as “multistrata homegardens.” Homegardens are “intimate, multistory combinations of various trees and crops, sometimes in association with domestic animals, around the homestead” (Nair & Kumar, 2006). Homegardens are most prevalent in the tropics—e.g., South and Southeast Asia, Pacific Islands, East and West Africa, Mesoamerica—but also exist to a much smaller degree in temperate zones of China, North America, and Europe (Nair & Kumar, 2006). Homegardens have been cultivated in tropical regions across the globe for centuries, or even millennia in some cases, and continue today to be a major source of valuable and nutritious food, fodder, medicine, fuel, and building materials. In addition, homegardens can deliver intangible benefits to owners and caretakers, such as beauty, quietude, and a sense of pride, hope, and self-confidence, especially as the homegardener experiments, adjusts, and learns through the process of establishing and maintaining a multi-functioning homegarden (Katanga et al., 2007). Finally, homegardens serve as both planned and associated biodiversity repositories (Montagnini, 2006), and they also sequester carbon.
As implied in the definition given above, homegardens are close to the homestead and consist of a number of intimate relationships. Homegardens are generally relatively small, up to 1.0 ha, though larger homegardens can occasionally be found (Peyre et al., 2006), and therefore relationships among the elements are usually managed intensively. Homegarden sustainability relies on the cultivation of these relationships for the efficient use of space, water, soil nutrients, and sunlight. Wiersum (2004) summarizes the benefits found by researchers working in the area of multispecies forest gardens, which are similar in structure (though not necessary similar in terms of caretaker goals and cultivation practices) to the homegardens of interest for this paper: (1) Efficient use of aboveground and belowground space, (2) efficient circulation of nutrients and reduced risks for depleting nutrients because of filters to protect against losses, (3) plant protection as a result of buffers against damaging insects and diseases, and (4) protection against potentially degrading forces such as torrential rainfall, surface runoff, or damaging winds, as a result of the presence of vegetative barriers.
Natural forests rely on the use of vertical space for the efficient use of light, soil nutrients, and symbiotic plant interactions; multistrata homegardens, too, rely on such use of vertical space. A forest is typically arranged in strata, or layers. The tallest trees combine to form a canopy, smaller tree species form an understory, a shrub layer fills the next stratum, and an herb layer fills the lowest layer of vertical space (Kricher, 1998). Fungi and organic litter (from leaves and twigs) form the lowest layer, and vines use the vertical architecture of the trees and shrubs to climb. Not all homegardens contain all these layers, though at least three layers are typically present (Jacke & Toensmeier, 2005; Kumar & Nair, 2004).
Jacke and Toensmeier (2005) write that the most productive stage in succession, in terms of net primary productivity, is intermediate succession, before the tree canopy closes in, when trees, shrubs, herbs, and vines all live together. The authors continue, “Luckily, most of our developed woody crops, including apples, pears, peaches, apricots, cherries, persimmons, raspberries, hazelnuts, walnuts, and so on, are adapted to such habitats” (p. 33). A homegardener can guide horizontal arrangement by creating patches of multistrata polycultures—allowing patches to slowly grow together as the tree canopy develops, which provides for years or even decades of harvests from smaller trees, shrubs, and herbs in the lower strata (more on this later in the paper). The horizontal spacing must be such that the trees and shrubs have plenty of room to grow outward without interfering significantly with other trees.
Kumar and Nair (2004) summarized the benefits of homegardens from an economic and/or social viewpoint, as compared with other farming systems under similar situations: low capital requirements and labor costs; better utilization of resources, greater efficiency of labor; diversified range of products from a given area; increased value of the components, leading to higher income and improved standards of living; increased self-sufficiency and reduced risk from climatic, biological or market impacts; better use of underutilized land; enhanced food and nutritional security; and increased fulfillment of social and cultural needs through product sharing and exchange. The authors were writing specifically about tropical homegarden systems, but smallholders in temperate zones certainly could enjoy many or all of these same benefits. While far fewer people make their living through subsistence farming in the developed world, creating complementary homegardens (Abebe et al., 2006) could result in yields of products (such as fruits, nuts, and herbs) with high nutritional value and high medicinal value (e.g., ginseng, elderberry), while also creating habitats for animals, improving environmental conditions, enhancing biodiversity, and sequestering carbon.
Homegardens reduce atmospheric CO2 levels via three main mechanisms: they sequester carbon in biomass and soil, reduce fossil-fuel burning by promoting woodfuel production, and help in the conservations of carbon stocks in existing forests by alleviating the pressure on natural forests (Kumar, 2006). In the context of increasing concerns about global climate change, finding cost-effective methods for sequestering carbon has become a major international policy goal (Montagnini & Nair, 2004). Homegardens sequester carbon in plant biomass and soil, and can be particularly effective if the soil is left relatively undisturbed, as soils contain the major stock of carbon in tree-based ecosystems. Sequestration of carbon in the soil occurs because more than half of the carbon assimilated via photosynthesis in the leaves is eventually transported below ground via root growth and turnover, root exudates of organic substances, and litter deposition (Montagnini & Nair, 2004). As compared to annual monocultures, long-rotation systems such as agroforests and homegardens sequester sizable quantities of carbon (Montagnini, 2006), as the amount of biomass—and, therefore, carbon—that is harvested and exported from the system is low compared to the total productivity of the tree (Montagnini & Nair, 2004).
Other Ecological Benefits
As discussed above, homegardens provide the opportunity for efficient nutrient cycling through species and structural diversity, constant ground cover, nitrogen fixation, symbiotic plant interactions, and long rotational timeframes. In the tropics, homegardens serve as repositories for biodiversity, both planned and associated. Planned biodiversity includes the collection of plants and animals that the homegarden manager has decided are part of the managed system, while associated biodiversity includes all other organisms not intentionally included in the managed systems, such as insects, frogs, birds, fungi, etc. (Perfecto & Vandermeer, 2008). Not only cultivated plants but also “weeds” can bring the number of “useful” plant species in a single homegarden into the dozens (Montagnini, 2006).
Though more properly considered a forest garden (Wiersum, 2004), Feldhake and Schumann (2005) experimented with a multistrata system, based on trees and shrubs only, in central Appalachia, U.S.A. The researchers planted a 1.2 ha forest clear-cut with red oak (Quercus rubra) as the mature forest species for future veneer logs, with alternating rows of Chinese chestnut (Castanea mollissima), pawpaw (Asimina triloba), hazelnut (Corylus Americana), and white pine (Pinus strobus), and interplantings of blackberry (Rubus spp.) and blueberry (Vaccinium spp.), for generating income as the forest matured. Though the study looked at tree growth, under a variety of growing conditions, for only four years, a couple of interesting author comments and research findings are germane to this paper. First, the authors state in the introduction, “In this high rainfall region, most of the nutrients are tied up in biomass on shallow-soil sites, thus site productivity may be compromised by frequent complete removal of the above-ground biomass” (Feldhake & Schumann, 2005, p. 187), indicating one of the major problems with traditional agriculture in that region. This type of system overcomes these limitations by improving on-site nutrient retention compared to traditional forestry or agriculture. Second, at the end of four years, the chestnut trees averaged more than twice as tall as oak, hazelnut, and pawpaw, and pawpaw had surpassed the oak in height. Given the slower growth rate of the oaks, the desired future canopy tree, the opportunity was created to provide short-term income from nuts and fruits for several decades while the oak canopy is developing (Feldhake & Schumann, 2005). One observation by this author is that Feldhake and Schumann give no indication that plants such as clovers or vetches were used in the herb layer, which could have led to improved nutrient cycling to aid the growth of the fruit and nut trees, through providing groundcover, mulch, nitrogen fixation, and dynamic accumulation.
As mentioned in the introduction, Nair and Kumar (2006) write of some examples of temperate homegardens in parts of China and Europe. Traditional homegardens in the temperate region of Isparta, Turkey, are used to grow fruits and vegetables for both home consumption (on average, about 1/3 of the production) and for market (about 2/3 of production), and are also used for raising animals for meat, eggs, and milk (Bassullu & Tolunay, 2010). Jacke and Toensmeier (2005) provide case studies of three homegardens in North America. As compared to the literature on tropical homegardens, of course, these examples seem paltry, though the applications are encouraging, nonetheless.
In uncertain times of increasing fossil fuel prices and climate change, diverse homegardens may provide ecological and socioeconomic sustainability for people living in temperate zones, as they do for people of the tropics. Given that approximately 80% of Americans live in cities, it has been argued that adoption of agroforestry practices should begin with urban populations and landscapes (USDA, 2011). Urban agriculture represents a continually growing activity, in both tropical and temperate climates, and in both developing and developed countries (Drescher et al., 2006), though the evidence is that urban agriculture in developed countries consists mainly of plantings of annual food crops (e.g., Patel (1996)). The adoption of multistrata homegardens, with a focus on perennials and woody plants, could work as well in these situations as it has in tropical regions.
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Bassullu, C., and A. Tolunay. (2010). Analysis on traditional homegarden involving animals practices and its importance classification of usage purposes in rural areas of Isparta region of Turkey [sic]. Asian Journal of Animal and Veterinary Advances, 5(7): 450-464.
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Peyre, A., A. Guidal, K.F. Wiersum, and F. Bongers (2006). Homegarden dynamics in Kerala, India. In Kumar, B.M. and P.K. Nair (eds.). Tropical Homegardens: A time-tested example of Sustainable Agroforestry, (pp. 87-103). Dordrecht, The Netherlands: Springer.
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Wiersum, K.F. (2004). Forest gardens as an ‘intermediate’ land-use system in the nature-culture continuum: Characteristics and future potential. Agroforestry Systems, 61: 123-134.
This article was excerpted from the original with the kind permission of the author:
Hill, M. 2012. Temperate Homegardens. Agroforestry Net, Holualoa, Hawaii, USA.
Michael Hill is a student of permaculture and agroforestry. He is currently taking graduate courses in agroforestry from the University of Missouri, and he holds a doctorate in research methodology from the University of Virginia. He lives with his wife and two children on the Asheville School campus in Asheville, North Carolina. He chairs the mathematics department at Asheville School.
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