Mary Heie, UM Extension Master Gardener in Anoka County, May 25, 2016
If you have some problem spots in your yard such as under trees or other shady areas where nothing seems to grow, consider using ground covers. Usually ground covers fill an area by runners, reseeding or underground rhizomes. If the desired plant doesn’t spread this way, you need to use several plants to fill the desired area. Some ground covers require full shade, others do best in full sun, and some seem to thrive regardless of where they are planted. Once established, ground covers require minimal upkeep and can add visual impact to your landscape, particularly if the area is filled with the same plant variety. A planting around a tree has the added benefit of protecting the tree from damage caused by lawn mowers and trimmers.
When planning the ground cover, consider the site, the soil and the desired effect. For sunny sites you can use plants such as: daylilies, yarrow (achillea), sedums, salvias and various grasses. Shorter plants that grow approximately 6 to 12 inches tall are effective, too, such as: yellow archangel (lamiastrum galobdolon); moneywort (lysimachia nummularia) and wineleaf cinquefoil (potentilla tridentate).
There are many, many possibilities for shady areas. A variegated hosta looks nice around an oak tree. Here are some other popular shade favorites. Periwinkle (Vinca minor) is a vining type of plant with blue flowers in the spring. The leaves are small and oval shaped. It sends out runners that will root where they touch the ground. It is easy to control. Japanese spurge (Pachysandra terminalis) grows about 6 to 8 inches tall. It has small leaves that are toothed at the ends. White flowers appear in the spring and early summer. It spreads by underground rhizomes. Both of these plants are evergreen and prefer shade and well drained soils. Bugleweed (Ajuga reptans) grows to about 3 or 4 inches tall. The leaves can be green or almost a bronze color. Flowers are blue to purplish in color. This plant will tolerate some sun. Sweet woodruff (Galium odoratum) is a mat forming ground cover for shade and grows to about 12 inches. It has small fragrant white flowers in the spring. Deadnettle (laminum) grows to about 6 inches tall and has green and white variation on the leaves. It spreads by sending out runners and flowers in the early summer. It seems to like either sun or shade.
Ferns are another great ground cover for shady areas and there are many varieties available. Two particularly nice ferns when planted in a woodland setting are the maidenhair fern (Adiantum) and Japanese Painted Fern (Athyrium niponicum).
There are some ground covers that can become invasive in the landscape: These include: Snow on the Mountain (Aegopodium podagraria); Lily of the Valley (Convallaria); Bishop's weed or goutweed (Aegopodium podagraria); and ribbon grass (Phalaris). These plants are not picky about growing conditions and most spread by rhizomes and seeds. Once established, they are nearly impossible to get rid of. If you must have one of these invasive plants, grow it in a contained area or in an area where an uncontained spread does not matter. For more information visit www.extension.umn.edu