Groundcovers may come in different shapes and sizes, but they all share several important attributes: many flourish in challenging conditions turf grass won't tolerate; once established, they act as living mulches by keeping soil temperatures cooler and out-competing weeds; and,
as a design element, they can connect disparate parts of the garden.
While traditionally thought of as ground-hugging plants, in fact, any specimen that grows vigorously and can be planted en masse is a groundcover candidate. Most will tolerate only light foot traffic; if you decide to use taller types, create narrow pathways through them to avoid treading on the plants themselves. Before choosing a groundcover, though, assess your landscape conditions. Cast-iron hardiness is essential, so select specimens hardy to one or two zones colder than where you garden.
Next, consider how much sunlight the area receives; gardeners tend to use groundcovers primarily in heavily shaded areas, but there are also many suitable for full sun situations. Finally, select plants that will be in scale with their surroundings: large ostrich ferns and hostas may be perfect under mature trees, but dwarf pinks and astilbes are more suitable around walkways and patios.
Preparing the site
Begin by clearing the site of turf grass and weeds, which may be done manually in smaller areas. Elsewhere, apply sheets of black plastic in late spring (heavy-duty garbage bags work well) held in place with bricks, wood or rocks. Over the next six to eight weeks, the plastic will smother the weeds and turf. Once the vegetation is dead, remove the plastic and cultivate the soil with a rototiller or garden fork. Finally, spread eight to 10 centimetres of organic matter (shredded leaves, compost, composted manure or a mixture) over the surface, then dig it in 20 to 25 centimetres deep.
Ready to plant
Before planting, help suppress weeds by applying an organic mulch (shredded leaves, finely chipped bark or wood), which will decompose before plants fill in, especially when growing small specimens. It's easier to plant straight through the mulch rather than adding it afterwards. (Be sure not to let it touch the plant stems.) Avoid large, coarse mulches—these take too long to break down, impeding the spread of the plants.
Spacing plants depends on the size and habit of the groundcover; however, place them close enough so they’ll fill in within two years. Rather than planting sparsely, start with a small, densely planted area and extend it in subsequent years with divisions from the original specimens. Space plants evenly so they’ll cover the ground at the same rate.
When planting, position specimens at the same depth at which they were growing in their pots. Water well. Fertilizers are unnecessary; as the groundcovers go dormant in the fall, their dead foliage will supply nutrients to the soil. In addition to rainfall, supplemental watering may be required in the first year as root systems become established.
In two years, when your groundcover has filled in, it should be fairly carefree. Shearing is seldom necessary but may be useful if plants become overgrown, or to encourage new growth and branching. Spring-flowering groundcovers should be cut back immediately after blooming, while summer- and autumn-flowering ones should be pruned in early spring before flower buds form.
Five great groundcovers
• Bugleweed (Ajuga reptans) 10 cm tall; part to full shade;
• Canadian wild ginger (Asarum canadense) 12 cm tall; full shade;
• Roman chamomile (Chamaemelum nobile) 8 cm tall; full sun;
• Least stonecrop (Sedum lydium) 4 cm tall; full sun;
• Thyme (Thymus praecox) 5 cm tall; full sun;