When Jack and Jill went up the hill, they didn't expect soil to come tumbling down around them, but this is the problem faced by gardeners with erosion problems. Planting low-maintenance, erosion control shrubs is one way of reducing the amount of soil on the kids' clothes after a day spent playing on the garden slope. Gardeners can also improve planting sites, spread suitable mulches, lay stones, and even build terraces to help prevent erosion.
Taking simple measures when planting and caring for shrubs plays an important role in effective erosion control. To provide a moisture-retentive environment for roots, mix garden compost or well-rotted manure into the soil in planting holes, and spread a 3- to 4-inch mulch of organic matter that won't wash away, such as mixed fir bark or vineyard mulch. Watering from hoses or sprinklers increases erosion, so either water shrubs with a watering can for the first year or install drip irrigation lines. Hard landscaping can include large stones, which are attractive landscape features, help prevent soil erosion and are useful stepping stones for access to plants, reducing the need for stepping on the soil.
Terraces convert hillsides into a series of level steps with low walls and reduce erosion problems dramatically. Making 2-foot-tall timber walls made of treated timber secured with metal spikes through drilled holes can be a straightforward project for a novice handyperson. Sink the lowest layer of timber to half its depth in the soil for stability, build the bottom wall, then shovel soil forward from the hillside to create a level bed. Another two-foot wall encloses the back of the first terrace, and the wall of the second terrace lies above it, fixed to it with spikes. The number of terraces required will be the height of the hill divided by two, and the depth of each terrace will be the distance along the slope divided by the number of terraces.
Evergreen shrubs for erosion control clothe the hillside in permanent green, their leaves softening the effect of driving rain. Mountain mahogany (Cercocarpus montanus) is covered in attractive silvery white tails that hang from its fruit in late summer, and in fall its leaves turn russet. Suitable for U.S. Department of Agriculture plant hardiness zones 5 through 10, it grows 8 to 12 feet tall and 4 to 8 feet wide. Inkberry "Shamrock"(Ilex glabra) is another evergreen with attractive fall fruit, bearing jet-black drupes that provide food for birds. Growing 3 to 4 feet tall and wide, it's hardy in USDA zones 4 through 9.
Spreading, deciduous shrubs hold the soil effectively on hillsides and provide beautiful fall foliage and fruit. Fragrant sumac "Gro-Low" (Rhus aromatica) grows 1 1/2 to 2 feet tall and 6 to 8 feet wide, spreading through root suckers. It bears hairy, red fruit, and its fragrant leaves turn orange and red in fall. Fragrant sumac is hardy in USDA zones 3 through 9. Snowberry "Hancock" (Symphoricarpos x chenaultii) grows to the same dimensions but spreads by growing roots where its arching stems touch the ground. It bears attractive, coral pink drupes and bell-shaped, white or pink summer flowers and is suitable for USDA zones 4 through 7.
- U.S. Department of Agriculture Natural Resources Conservation Service: Backyard Conservation -- Terracing
- University of California Sonoma County Master Gardeners: Gardening on a Hillside
- Missouri Botanical Garden: Cercocarpus Montanus
- Missouri Botanical Garden: Ilex Glabra "Shamrock"
- Missouri Botanical Garden: Rhus aromatica "Gro-Low"
- Missouri Botanical Garden: Symphoricarpos x chenaultii "Hancock"
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