- The ideal ground cover reduces soil erosion, excludes weeds, and is attractive year-round.
- When selecting a ground cover, consider the size of the area, exposure, steepness of slope, foot traffic and soil condition.
- Most ground covers require at least two years to provide serviceable cover.
- In some situations a “nurse crop” may be desirable to provide immediate soil stabilization on steep slopes.
- At high elevations, plant seeded ground covers in the fall or spring. Rooted plants are best planted in the spring.
- The ideal ground cover plant forms a sufficiently dense mat of roots and foliage to reduce soil erosion, exclude weeds and provide an attractive, year-round appearance. A ground cover, by definition, spreads. Species that spread by rhizomes (underground stems), stolons (like the “runners” on strawberries), offsets (“splits”), or rooting of branches (tip-layering) generally are best for ground cover.
Sod-forming grasses fit most of the above requirements and have the additional benefit of withstanding considerable traffic abuse. There are situations, however, when grasses may not be desired for aesthetic reasons or where mowing and other turf maintenance are not practical.
No one species of ground cover plant is the solution to every landscape or soil stabilization problem. No ground cover is free of faults. Before selecting a plant for ground cover, consider the following items:
- Size of area to be covered. Ground covers are not limited to low, creeping types. When attempting to cover large areas, use shrubs that grow to 3 or 4 feet.
- Exposure. Select plants that thrive best under the site’s sun, shade and wind conditions.
- Steepness of slope. For steep grades, use species that produce dense, fibrous roots to help prevent soil erosion.
- Pedestrian traffic. Few ground covers, other than grasses, tolerate repeated foot traffic.
- Drainage and aeration. Surface soils may appear loose and loamy, but heavy, poorly drained subsurface soil may be present. Few ground covers thrive in poorly drained soils. A heavy clay soil on a steep grade has poor subsurface drainage and poor aeration.
- Maintenance. Most ground covers require at least two years to establish themselves and become sufficiently dense to control weeds. At higher altitudes, most ground cover plants take three or more years to provide serviceable cover. None can be completely neglected even after the planting is well established.
During abnormally dry periods, even established ground cover plantings benefit from supplemental water. Without it, the planting may thin out and allow weed competition. A distinct disadvantage of most ground covers, other than grasses, is the lack of selective weed control chemicals. Maintaining the cover as a dense stand is, therefore, of utmost importance to reduce or exclude weeds.
Ground cover plants spread best when the soil is loose and loamy. Add organic matter, such as peat, compost or aged manure, to improve heavy clay soils or light sandy ones. Such amendments help absorb and hold moisture and contribute to better aeration and nutrition. Thoroughly work the organic matter into the soil to a minimum depth of 6 inches.
A “nurse crop” of grasses and legumes may be needed to provide immediate soil stabilization on steep slopes. The nurse crop depends on elevation, exposure, type of permanent ground cover desired, and availability of supplemental water.
Select the nurse crop carefully. The wrong one may become too aggressive and compete with the permanent ground cover.
Nurse crops are best planted in early spring or late fall when natural rainfall and snows are most likely. Avoid planting during hot, dry periods unless supplemental water can be provided.
Prepare soils as suggested in the section on soil preparation. After seeding, lightly rake the area to help place seed in close contact with the soil. If available, cover with a 1/4-inch layer of mountain topsoil, peat, straw or similar material. Commercial hydromulch also may be available in your area.
Planting Ground Covers
Plant ground covers in the same manner as annual and perennial bedding plants. Spacing varies with the type of plant. Planting too close together usually is worse than planting too far apart – the plants will crowd too quickly, restricting spread. Water newly planted ground covers immediately after planting. The first growing season is the most critical in getting a ground cover established. Keep the soil in the root zone moist but not too wet. Too much moisture can slow root growth and may encourage disease.
Except for plants established from seed, avoid fall planting. Plant as early in spring as the soil can be worked to allow time for root growth before cold weather arrives.