Use a mix of groundcover, trees, shrubs and perennials planted across a hillside to get the best protection against erosion. Cover any exposed ground in between plantings with mulch or boulders. Rain that falls will hit the plants, boulders and mulch first, slowing the rate at which water can hit and be absorbed by the soil underneath. Larger plants will have complex root systems, better protecting the hillside. Plants with large leaves can help against wind erosion.
Types of Plantings
A mix of deep-rooted plants are necessary to bind the topsoil to any rock formations underneath. It's crucial for the top 1 to 2 feet of soil to be tightly bound together. Evergreen huckleberry is a shrub that can reach 6 feet and grows a thick fibrous root system in the upper layers of the soil. The blue rug juniper shrub is a low-growing, low maintenance ground cover that is known for erosion control. Sumac shrubs are also a popular choice for erosion control. All of these plants are meant for growing zones 3 through 9 across the country, but using plants that are native to a certain locality will best thrive and blend into local landscaping.
Types of Mulch
Mulch is the covering used to control erosion on exposed soil between plants. The best mulch to use on a hillside is shredded bark or wood chips. Landscape trimmings, compost, straw and shredded paper are not recommended for use as mulch in erosion control, as they do not bind well to soil and may just wash away with it.
Drainage and Slope
Hillside areas are more unstable when drainage is poor. A very steep slope can also contribute to erosion problems. A more aggressive approach than plantings, such as installing a retaining wall or a dry creek bed, may be necessary if either of these factors is present. A retaining wall is typically made of loose stone or decorative brick and will capture water and let it slowly percolate down into the the soil. Using a series of small terrace walls is often a better solution than building one large retaining wall, as a larger wall can often require a permit. Installing a dry creek bed, in which water collects and is redirected down a designated path to an appropriate outlet further prevents erosion control.