When landscaping on a hillside with trees or shrubs, proper planting is key. Taking a few extra steps during planting will ensure that your landscaping stays put and grows strong. When planting on a slope, the roots and trunk should be vertical; and the ground modified, so water is directed to the plant’s roots, rather than running straight off.
Follow these steps when planting trees and shrubs on a slope.
Step 1: Build Terrace
Create a flat area or small terrace in your slope, about three times the diameter of the root ball of your tree or shrub. You can create this terrace by:
- Combination of cutting into and building out the slope.
The less you disturb the original soil, the more stable your slope will be. The finished terrace should be firm enough to stand on while working.
Step 2: Plant Tree or Shrub
Now that you have a nice flat spot, plant your tree or shrub with the trunk upright and vertical and the root ball at the proper planting depth. Position your planting hole near the center of the terrace, and try to leave some undisturbed soil on the downhill side to keep from having the following problems:
- If the plant is too close to the top of the slope, it may become buried by soil or debris tumbling down the hill.
Step 3: Create Berm to Hold Water
As you backfill around your tree or shrub, put the excess dirt on the downhill side to create a small berm to catch water as it runs down the slope. Make sure not to pile extra dirt directly on the root ball, but make a “half-donut” shape around the plant instead.
Step 4: Apply Mulch
Put about 2-3 inches of mulch around the tree or shrub to help hold the dirt and berm in place, keeping the mulch a few inches away from the trunk. If you’d like, you can first put down a layer of landscape fabric or mesh held firmly in place with garden staples. Be sure to choose non-slippery landscape fabric, so your mulch won’t slide off.
Step 5: Water Plant
Water your tree or shrub well to help settle the soil. Fix any problems that arise after the first watering, to make sure the planting is stable.
Step 6: Monitor Plant
Keep an eye on the tree or shrub for a few months to make sure the soil is settling properly, water is being captured, and the roots are staying in place. Make sure the roots aren’t being buried by falling debris, and the berm stays in place for at least a year or two, until the plant is well established. Reapply mulch as needed to help hold water.