Most traditional groundcovers are perennial, including English ivy (Hedera helix), pachysandra (Pachysandra spp.), and common periwinkle (Vinca minor). But some perennials, used mostly in garden settings, also make great groundcovers. These plants are attractive in and of themselves, but they have the calssic groundcover traits: they're low-growing, they spread quickly, and they form a dense cover that resists weeds. These perennials include ajuga (Ajuga reptans), spotted lamium (Lamium maculatum), and yellow archangel (Lamiastrum galeobdolon), all of which have cultivars with variegated foliage; ajuga alsk has bronze- and purple-leaved cultivars.
Some of the most delightful perennial groundcovers grow best where you need them most; in the shade under trees. These include the wild gingers (Asarum spp.), with their beautiful matte or glosse green foliage; sweet woodruff (Galium odoratum), with whorled leaves; green and gold (Chrysogonum virginianum), with bright-yellow flowers; delightfully fragrant lily-of-the-valley (Convallaria majalis); and violets (Viola spp.), with their characteristic heart-shaped foliage.
Variegated bishop's weed (Aegopodium podagraria "Variegatum") grows vigorously in sun or shade; make sure it can't invade your perennial border. If you need plant cover between stepping stones or in a sunny, rocky site, try one of the creeping thymes like the soft, silvery woolly thyme (Thymus pseudolanuginosus), or fragrant chamomile (Chamaemelum nobile). Other perennial groundcovers that like sun are the woolly white lamb's-ears (Stachys byzantina); cranesbills (Geranium spp.), with wonderful palmate foliage and colorful flowers; and leadwort (ceratostigma plumbaginoides), with bright-blue flowers and leaves that flush red in fall.
Beacause most perennial groundcovers have showy flowers as well as handsome foliage, they add color and life to dark areas as well as amking sunny areas more interesting. But as with all groundcovers, you usually need many plants to make a visual impact. That makes perennial groundcovers ideal candidates for the nursery bed; an area that's been set aside specifically for propagation and growing young plants. You can grow seedlings in the well-prepared soil of this protected area, or buy and establish stock or mother plants in the nursery bed, then take cuttings or root runners.
These versatile groundcovers look lovely in the perennial garden, but they can also stand on their own. Use them along a walk to soften the straight edges, under trees to brighten a shady area, around a pool, or anywhere you don't want the high maintenance lawn grass requires.
Bearberry (Arctostaphylos uva-ursi) - small, glossy, evergreen leaves on low, spreading plants; pink, bell shaped flowers in spring; sun or partial shade.
European wild ginger (Asarum europaeum) - glossy, kidney-shaped leaves; 7 inches tall; shade.
Lily-of-the-valley (Convallaria majalis) - fragrant white or pink, bell-shaped blooms in spring; sun or shade.
Bunchberry (cornus canadensis) - white flowers in spring above whorls of leaves; 6 inches tall; shade.
Epimediums (Epimedium spp.) - dainty heart-shaped leaflets; flowers in spring; shad.
Hellebores (Helleborus spp.) - divided leaves; evergreen; to 24 inches tall; green, white, pink or purplish flowers in winter or spring.
Houttuynia (Houttuynia cordata) - red, pink, and white variegated or solid-green heart-shaped leaves; 1.5-3 feet tall; sun or shade.
St.-John's-wort (Hypericum calycinum) - characteristic heart-shaped foliage.
Lilyturf (Liriope) - clumps of grass like leaves; white or purple flowers; 1-1.5 feet tall; sun or shade.
Creeping Jenny (Lysimachia nummularia) - creeping plant for moist soil, 2-4 inches tall; small rounded leaves; yellow flowers; sun or partial shade.
Sedums (Sedum spp.) - 2-24 inches tall; thick, succulent leaves; flowers in white, yellow, pink, or red; sun or partial shade.
Allegheny foamflower (Tiarella cordifolia) - heart-shaped leaves; white, fluffy flowers.
Barren Strawberries (Waldsteinia spp.) - evergreen, strawberry-like leaves; yellow flowers; 8-12 inches tall; sun or shade.