Retaining walls provide stability and prevent soil erosion in areas with hilly or uneven ground. The building materials can make retaining walls attractive landscape features, but they are ideal for dressing up with flowers. Walls with growing space at the top rather than the bottom can be more challenging to find plants for, but there are many cascading flowers that add color to these types of walls.
Creeping Jenny (Lysimachia nummularia) is a perennial that grows in U.S. Department of Agriculture plant hardiness zones 3 through 8. It prefers moist soil and full sun but will grow in partial shade, as well. Golden flowers bloom in early summer, and the round leaves are striking with or without blossoms. It can grow over other plants and smother them, so give it plenty of space to spread out.
Ground morning glory (Convolvulus sabatius) comes in a wide range of colors, making it a versatile flower for retaining walls. It is perennial in USDA zones 7 through 9, but can be grown as a summer annual across the rest of the country. Once it is established it needs little water or maintenance. The bell-shaped flowers emerge in spring and continue to bloom all summer.
Silver Lace Vine
Clusters of small, creamy white flowers with heart-shaped green leaves make silver lace vine (Polygonum aubertii) a memorable addition to a retaining wall. This rapidly-growing plant is hardy in USDA zones 5 through 9 and blooms twice -- in late spring and again in early fall. Silver lace vine requires full sun and regular watering. It is heat-tolerant, drought-resistant and will grow in poor soil.
With vines that can grow up to 30 feet long, trumpet vine (Campsis radicans) is ideal for tall retaining walls. It grows in USDA zones 4 through 10 and may be planted year-round in zones 7 and up. The plant is named for the trumpet shape of its brilliant orange flowers which develop into a pod-shaped fruit. Trumpet vine is easy to grow but may require pruning to keep the long vines contained. It can become invasive in some areas due to its rapid growth, so it should be planted where it will not take over other plants. It tolerates slightly alkaline, acidic or clay soils, is drought-resistant and requires full sun for maximum flower production.