Not all gardeners like the look of mulch under their shrubs and trees. Ground covers are a good alternative. Once they've filled in, ground covers do an excellent job of discouraging weeds. Use care when choosing a ground cover, however; the cultural needs for both ground covers and larger plants should be similar. Also avoid aggressive vines like ivy (Hedera) and Virginia creeper (Parthenocissus quinquefolia) which grow up into shrubs and smother them.
Goutweed (Aegopodium podagraria), also called bishop's weed and snow-on-the-mountain, is adaptable to a wide range of light and soil conditions. Variegatum is the most commonly seen cultivar in garden centres and is available in flats in spring. Goutweed is an aggressive spreader and is best used in contained beds rather than mixed shrub and perennial borders. The green and white leaves bring a touch of lightness to dark corners. Early summer white flowers are an added bonus. The dense, deciduous foliage grows 6 to 12 inches tall.
Tough and evergreen, periwinkle (Vinca minor) is a common ground cover for shady spots. The glossy leaves are topped with blue or white flowers in spring, with occasional reblooming throughout the summer. Trailing stems spread rapidly to form a dense, 3- to 6-inch carpet. Several cultivars are available, including Illumination, a new introduction with gold variegation on the leaves. Alba is a commonly sold white variety and Alba Plena has white, doubled flowers. Vinca needs good drainage to thrive.
Also called yellow archangel, dead nettle (Lamiastrum galobdolon) is a fast-spreading herbaceous ground cover that's very shade tolerant. The variety Herman's Pride is slower growing than the species, with a neat, mounding habit. Dead nettle has yellow flowers in early spring and many cultivars have variegated foliage. Lamiastrum reaches 12 to 18 inches in height, so it's a better choice for under trees than for low-growing shrubs.
Most gardeners only consider hostas (Hosta spp.) for specimen plants in shady perennial gardens, but the smaller varieties also make excellent ground covers in shade. Small cultivars to consider include Kabitan, with narrow, green and yellow leaves, and Golden Tiara, with gold-rimmed, heart-shaped leaves. Hostas are tolerant of dry shade once established, making them a good choice for planting under trees.
Establishing Ground Covers in Shade
Unless you're planting ground covers at the same time you're establishing the planting bed, you'll disrupt the roots of existing plants less by using small plants or plugs. Mulch around ground covers until they fill in well enough to shade the ground and prevent weed growth. Soil under large shrubs and trees is often poor and dry, so water and feed ground covers the first season or two, until they're well adapted to their location.