Slopes are difficult areas to plant, maintain, and irrigate. Soils on south and west-facing slopes with considerable sun exposure dry quickly, and storm water runoff can significantly increase erosion problems.
Consider water-conserving plantings for these tough spots. Appropriate shrubs, perennials, and groundcovers are available at local garden centers.
Steep slopes will initially need to be stabilized to prevent loss of soil and water by erosion. Ground covers and other plantings can be planted on slopes to reduce erosion. Drip irrigation is the most effective way to efficiently provide water to plants on slopes.
Retaining walls are effective ways to stabilize and visually improve slopes. A variety of usable spaces on different levels can be created using terracing. Access for maintenance and irrigation is made easier. A formal or informal look can be created. Use plant species adapted to hot, dry, and rocky sites.
Additional Resources:
West
Colorado: Xeriscaping – Retrofit Your Yard
Southeast
Mississippi: Gardening on Steep Slopes