Ground covers are low-growing, creeping plants; they help prevent erosion on hillsides as their shallow root systems hold the soil in place during a rain. Since ground covers are low to the ground, they can handle even the steepest slope without adverse effects. Evergreen ground covers will provide a year-round lushness and color to sloping terrain. Try bearberry (Arctostaphylos uva-ursi), candytuft (Iberis sempervirens), creeping juniper (Juniperus sp.) or Japanese spurge (Pachysandra terminalis).
For more structure on a slope, consider a terraced bed. Install a terraced bed by digging into the hillside to create a level area. The initial work is the most difficult. Install hardscaping material such as bricks or landscaping stones around the front of the terraced bed to establish a border and to hold the soil in place. Plant back from the border of the bed, starting with low-growing plants and placing a larger shrub or two next to the slope. Fill in empty spaces with annuals.
Create the illusion of more than you have by creating a group of dramatic specimen plants at the base of the slope. Choose an odd number of larger, showy shrubs such as Rose of Sharon (Hibiscus syriacus), bigleaf hydrangea (Hydrangea macrophylla), bridalwreath spirea (Spiraea prunifolia), Chinese fringeflower (Loropetalum chinenens), or common lilac (Syringa). Plant as many as space will permit to create a lush feel. Plant smaller perennials or annuals at the base of these shrubs, then plant ground covers toward the slope and train them to grow up the hill.