Retaining walls are an important landscaping feature used to bolster hills and mounds of dirt so that rain does not lead to a mudslide. Massive retaining walls can be found on the sides of highways, but most home retaining walls range from a few inches to a few feet high. If your yard features a stark, unattractive retaining wall, planting the right plants along the top can hide or decorate it.
Moss often naturally grows on retaining walls whether you plant it there or not. Only moss can completely cover the surface of a rock or brick wall. Choose varieties that can handle the dry and sunny conditions of most retaining walls, such as Orthotrichum pusillum, since most mosses prefer damp and shaded conditions. Moss can be encouraged to grow on a retaining wall by being mixed in a blender with yoghurt or buttermilk says the World of Mosses website. When this mixture is sprayed on the wall's surface, it sticks and allows the moss to develop a new colony.
Fast growing, spreading ground covers will create a mat of greenery along the top of a wall. Dianthus gratianopolitanus, also known as Firewitch Dianthus, is recommend by the Purdue Extension due to it's hardy nature and low maintenance. It grows in zones 3 through 9 and requires full sunlight and well-draining soil. Phlox subulata, or creeping phlox, also works well due to its shallow roots that won't damage the wall and 6 inch maximum height. It is hardy in zones 3 through 9 and requires full sun.
If the wall has a rough texture or you choose the right plant, you can cover the face of a retaining wall with climbing vines. Bluebill and Virginia creeper are both recommended by the Ladybird Johnson Wildflower Center. Clematis pitcheri, also known as bluebill, can climb a rough stone wall and produces long lasting blue flowers. It requires full sun and well-draining soil and is hardy in zones 4 through 9. Virginia creeper, or Parthenocissus quinquefolia, will grow on smooth retaining walls. It can handle zones 5 through 11 and will grow in either full sun or full shade, as long as the soil offers good drainage.
Plants that grow long trailing stems will soften the top edge of the retaining wall. Vines that aren't strong enough to climb the wall can be used to drape over the edge instead. Old man's beard, also known as Clematis virginiana, is a good choice due to its fast-growing vines and white blossoms, says the Ladybird Johnson Wildflower Center. It thrives in any light condition and can handle dry or moist soil; it is hardy in zones 5 through 7.