Gardening on a Steep Incline
A steep incline isn’t the easiest place to create a garden, but it is one of the most critical areas to plant. Unsecured soil washes off with every rain, but once roots start growing, they form a dense web that holds the soil in place. For variation and added protection against erosion, plant a combination of low-growing groundcovers, small trees and shrubs.
Before you start gardening on a steep incline, clear the area and prepare the soil with organic amendments. Remove weeds, grass and any unwanted plants, then spread 2 to 3 inches of compost or leaf mold over the soil. Dig the amendment material into the top 12 inches of the soil using a hand-held garden fork. While tillers work on slight slopes, they are difficult to control and dangerous on a steep incline.
Plant Selection and Spacing
Sloping land retains less water than flat areas. Select and plant drought-tolerant shrubs, trees and perennials to reduce water needs. Check the sun exposure on the incline. Full sun plants need at least six hours of direct sun, while part shade plants prefer 2 to 4 hours of sun. Plan for 3 feet of space between small 5-foot tall shrubs and 7 to 8 feet between 6- to 10-foot tall shrubs. Space groundcover plants 6 to 12 inches apart.
Site Access and Planting Time
When a steep incline is difficult to reach for planting and working, lay a ladder against the hillside to provide a makeshift scaffolding to work from. Secure the ladder firmly at the top and bottom to avoid slipping and falling. Plant new shrubs in the fall and winter rainy seasons whenever it is possible. Spring, summer or early fall planting require frequent water for the first growing season. You will need access to water regularly for the first growing season.
Planting on a Slope
On a steep slope, the angle of the planting hole is critical. It’s important to dig the hole straight rather than in line with the sloping soil, otherwise plants grow at an angle, which you want to avoid. Dig the hole so that the side on the downward edge is the same depth as the nursery pot. Dig out the soil on the inside of the hole so that the planting area has few inches of flat soil around it. Set all plants so that they are vertical, not in line with the slope, and fill in the soil around them.
Moisture and Mulch
Lay a soaker hose on the slope around the base of each new shrub to keep from drying out on the fast-draining slope and reduce the need to hand water difficult areas. Mulch after planting using shredded pine or redwood mulch. Avoid chunky mulch, like wood chips, which will roll off the side of the slope. Spread the mulch 2 to 3 inches deep over the exposed soil, leaving a 3-inch diameter area clear around the base of each plant. Reapply the mulch once a year to maintain a consistent 2- to 3-inch deep layer.
- University of California Sonoma County Master Gardeners: Gardening on a Hillside
- Alden Lane Nursery: Planting a Shrub or Tree on a Slope
- USDA Natural Natural Resources Conservation Service: Ground Covers for Steep Slopes
- Proven Winners: Make Your Bed
- Sunset: Planting Groundcovers
- Washington State University Spokane County Extension: Spacing Landscape Plants
Eulalia Palomo has been a professional writer since 2009. Prior to taking up writing full time she has worked as a landscape artist and organic gardener. Palomo holds a Bachelor of Arts in liberal studies from Boston University. She travels widely and has spent over six years living abroad.