It's hard to know what to plant on a slope. Slopes that are too steep to safely mow can become eroded and turn into an eyesore filled with weeds and invasive flowers and shrubs.
The key is to select the right plants for the slope and to maintain them well. Here are some plants to consider.
Most gardeners want low growing, creeping plants to cover a slope, but not turn into a jungle. For shrubs, one of the best are low growing junipers. Varieties, such as 'Blue Rug' and 'Bar Harbor', slowly spread over time. The evergreen foliage breaks the rain so less erosion occurs and it blocks the light so fewer weeds germinate. 'Gro Low' Sumac is a colorful creeping shrub. This sumac has deciduous leaves, and the stems creep and root along a slope holding the soil. The foliage turns a brilliant red in fall. Forsythia and cotoneaster are good bank holders. For best results, choose dwarf forsythia, such as 'Arnold's Dwarf', and cotoneasters, such as 'Little Gem', that only grow a few feet tall.
Grow perennial flowers on slopes that are less steep and can be managed. Common evergreen ground covers, such as vinca and pachysandra, are good, but they can also spread into other gardens nearby. For shady, damp slopes try the interrupted fern. It only grows 2 feet tall and spreads by rhizomes.
When planting, cut back all the existing plants on the slope but don't remove them. Dig holes to plant. Once your plants are established, slowly start removing the other weeds allowing your desired bank side plants to spread and thrive.