Landscaping Hillside Ideas
Plant a variety of low-maintenance shrubs to stabilize a hillside garden.
Hillside landscaping presents several challenges to gardeners. Plants must hold soil against erosion caused by wind, water or both. Access for plant care may be difficult. Environmentalists and landscapers advise that selecting several kinds of soil-holding plants, shrubs and trees is more effective than a single, or monoculture, choice. Several types of shrubs hardy to United States Department of Agriculture plant hardiness zone 9 meet hillside challenges well.
Large Blooming Shrubs
Four hybridized native shrubs make good low-maintenance slope-stablizers. Commonly called “California lilac” (Ceanothus spp.), ceanothus contains a wide range of blooming shrubs from 3 to 8 feet in height. A creeping variety (C. “Joyce Coulter”) is 2 feet high with a horizontal spread of up to 8 feet; C. “Ray Hartman” can reach 20 feet in height. Ceanothus is covered with abundant blooms in blue, violet or white throughout summer into fall. Plants are highly drought-tolerant and deteriorate severely when watered. Another drought-tolerant genus, evergreen manzanita (Arctostaphylos. spp.) comes in many white-flowering varieties, many of which are approximately 3 to 6 feet in height and width. Cleveland sage (Salvia clevelandii) is only one member of the large Salvia genus, many of whose members tolerate both full sun and dry soil. Cleveland sage is distinguished by fuzzy-looking gray-green leaves and large purple flowers and grows from 3 to 5 feet high.
Large Berried Shrubs
Common elderberry (Sambucus nigra) is a widespread American shrub with edible berries, treasured by pioneers and loved by birds. Reaching heights and widths of up to 6 feet, its deciduous foliage is accompanied by small clusters of white flowers, followed by blue-black berries. Common elderberry is highly adaptable, tolerating both moist and dry conditions and full sun to partial shade. Toyon (Heteromeles arbutifolia), also known as Christmas berry, is also flexible about moisture. Reaching up 15 feet or higher in the wild, toyon is usually 6 to 8 feet high in the garden, with a horizontal spread of up to 20 feet if left untrimmed.
Shrubs reaching 3 feet or less in height contribute additional textures and colors to a hillside landscape. California sagebrush (Artemesia californica) has feathery silver-green foliage and is highly drought tolerant. Dwarf coyote brush (Baccharis pilularis DC) reaches 1 to 2 feet in height with a horizontal spread up to 12 feet. This evergreen has dark green foliage and benefits from watering during dry spells. Oregon grape (Mahonia spp.) is a glossy-leaved evergreen that comes in both upright and creeping form; berries attract wildlife.
Shade-Tolerant Hillside Shrubs
Oakleaf hydrangea (Hydrangea quercifolia) can reach 6 feet in height. Lobed foliage and white-to-pink panicled flower clusters give this shade-tolerant deciduous shrub seasonal interest from spring through fall. For moist shade, common sweetshrub or Carolina allspice (Calycanthus floridus) grows to between 6 and 12 feet. Both deciduous foliage and spring-to-summer flowers are fragrant. Pacific rhododendron (Rhododendron macrophyllum) is evergreen and shade tolerant; varieties range is size from 5 to 25 feet.
Some communities and counties with frequent periods of dry hot weather regulate shrub planting, especially on large hillsides or other dry or windy areas, to reduce the danger of wildfire spread. These regulations limit plant choices and location even on private property in potentially wildfire-vulnerable areas.