Second only to turf grasses, ground covers are the category of plants most commonly found underfoot. Ground covers offer attractive, low-maintenance complements or alternatives to bluegrass turf. With a minimum of research and simple planting methods, new gardeners are rewarded with carpets of low-growing foliage. Well-established gardens often are anchored with textures suited to sunny or shady microclimates. Ideal ground cover plants will form a sufficiently dense mat of roots and foliage to reduce soil erosion, competitively inhibiting weeds while linking ornamental plants in the landscape. They provide a variety of shapes, patterns and colors, reduce soil erosion and add visual interest to transitions between turf areas and shrub or flower borders. Many ground covers go through a blooming season or change colors as temperatures drop in autumn.

Ground cover masses serve five basic functions:

1. Slope plantings. Turf grass is difficult to maintain on a steep slope, impractical to mow and difficult to irrigate uniformly. Vigorous ground covers choke out many weeds and fill those steep grades best left alone.

2. Combining with pavers, stones and paths. Hardscape elements can create a stiff and harsh appearance in the landscape. Planting ground covers around them softens that lowest plane of landscape design.

3. Filling shady areas under trees. Mature trees create both deep and dappled shade. Most turf grasses are not adaptable to such locations. Ground covers more effectively replace thinning turf and bring subtle rhythms to shady zones.

4. Providing texture, color, and height contrast with turf. Large expanses of turf can be attractive, but offer one-dimensional appeal. Masses of groundcovers placed next to turf introduce contrasting colors and textures, adding interest and diversity to the landscape.

5. Turn “hell strips” into gardens. Hell strips are areas between sidewalks and curbs or dry areas along south- and west-facing walls or fences, where growing anything is a challenge. Though often planted with turf, a more reasonable approach may be to introduce layered ornamental plantings that include sweeps of ground covers. Most ground cover plants effectively reduce maintenance work and add a finishing touch to landscaping projects. Well-established ground covers generally require less maintenance than turf grass lawns. Selected correctly, ground covers offer alternatives to lawns, requiring less maintenance and less water. But ground covers are not totally maintenance-free. They require routine fertilization, watering, weeding and pruning to develop into attractive plantings.

Designing with Ground Covers

The concept of “right plant, right place” is as important for ground covers as it is for all other types of plants. Placement and selection is crucial to the sustainability of any design. In most landscapes, the most important selection criteria are hardiness zone, growth habit, rate of spread, color and texture.

As design elements, ground covers work best as unifying features in garden beds. Repeating ground cover masses can be helpful aesthetically, as well as easing maintenance. Using more groups of fewer cultivars tends to unify the overall landscape, creating a more pleasing look than crowding too many varieties of plants into each section of the landscape.

The colors and textures offered by ground covers give gardeners a broad range of choices. There is a wide array of foliage textures and colors, as well as seasonal flowers and showy fruit.

Although some ground covers are damaged by traffic, if positioned with pedestrian movements in mind, they may function as traffic barriers. Unlike turf grasses, they may not invite you to walk upon them yet are low enough to not impose a visual barrier. In this capacity, they give the added benefit of keeping lawnmowers and string trimmers away from valuable woody and herbaceous plants.

When selecting ground covers, consider the plant's height, spread, blooming period, seasonal color, texture, drought tolerance, and whether it is deciduous or evergreen. Planting sites will affect your choices, because each ground cover has specific requirements.

Planting

Most ground covers can be planted anytime during the growing season; however, spring and fall are preferred because they offer nearly ideal growing conditions. Summer planting may require significant irrigation. Plant ground covers in the same manner as annual and perennial bedding plants. Spacing of plants will vary with the type of plant. Planting too closely usually is worse than too far apart because plants will crowd too quickly, restricting spread. The first growing season is the most critical in getting a ground cover established. Water ground covers immediately after planting. Keep soil in the root zone moist but not too wet. This can slow root growth and may encourage disease.

Planting Slopes

When planting slopes, it is critical to keep soil in place until plants are able to better control erosion. Dig planting pockets rather than completely tilling the bed, to help keep soil in place. Staggered plantings help prevent water from running off in straight lines. Mulch the entire area once plants are in place. Use anchor netting such as jute to hold plants and mulch in place. Jute fabric can be unrolled from the top of the hill and held in place with wire staples or coat hangers cut and bent into U-shaped fasteners.

Spacing

No hard and fast rules can be given for proper spacing of ground cover plants. The number of plants needed depends on the spacing of individual plants, their rate of growth and how fast you want the space to fill in. Recommended number of plants per 100 square feet, by ideal planting distance:

Fertilizers

An all-purpose fertilizer should be added at the time of bed preparation and planting. A 5-10-10 or 10-10-10 (nitrogen-phosphorous-potassium) fertilizer worked into the soil at planting provides a good start. A reasonable amount of 5-10-10 is 4 to 5 pounds per 100 square feet. If using 10-10-10, use 2 to 2 1/2 pounds per 100 square feet.

Annual fertilization of ground covers may or may not be necessary; plant performance is the key to making this call. Fertilize once a year in areas where additional growth among sparse plantings is desired, in late fall when plants go dormant (late October-early November). The application rate mentioned above is a good starting point.

Weeds

Control weeds to enable newly planted ground covers to form a dense mat. When properly established, ground covers can successfully compete with weeds. Until newly planted ground covers are dense enough to compete aggressively with weeds, hand weeding (especially early in spring) is probably the best option. Walking through the garden weekly and immediately pulling weeds is recommended.

A few pre-emergent herbicides are labeled for use with specific ground covers. It is critical that you read the label before application. Your specific ground cover must be listed for safe and legal use of the product. An application of a pre-emergence herbicide after the soil warms to 55 degrees Fahrenheit can be very helpful in reducing laborious hand pulling. Trifluralin is a pre-emergent herbicide readily available to homeowners. Some perennial weeds, such as thistle and bindweed, are difficult to remove by hand weeding because of regeneration from root fragments. These may be treated with a nonselective broadleaf herbicide applied with a brush, cloth or wick applicator. Care is advised since these herbicides will kill ground covers if applied to their foliage.

Mulching

Mulching serves many purposes in planting ground covers. Two to four inches of mulch around plants helps control weeds, moderates soil temperature extremes, conserves soil moisture and reduces erosion on slopes. Compost, leaf mold, well-rotted manure, bark or wood chips and peat moss can be used as mulches. In addition to these benefits, organic mulches add organic humus to the top layer of soil. Humus helps improve soil structure, water retention and oxygen diffusion.

Mulching helps to protect plants from winter injury resulting from uneven soil temperatures and soil heaving. Most evergreen ground covers need protection from winter drying. Two to 3 inches of organic mulch will reduce evaporation of moisture from the soil. Mulch helps prevent plants from heaving out of the ground as soil alternately freezes and thaws.

Mineral Mulches

Crushed stone, gravel, or volcanic rock can be used in rock gardens or if increasing organic matter content of soil is not a concern. Mineral mulches are very persistent, do not harbor weed seeds or diseases and are not blown about by the wind. However, they are not suitable for many ground cover areas. Unless underlaid with a landscape fabric (generally not a recommended practice), rocks migrate down into the soil over time. Individual particles can be thrown by lawn mowers, possibly causing injury.

Landscape Fabrics

Landscape fabrics have their drawbacks. Although fabrics allow water and oxygen to penetrate and inhibit some weed growth, over time weeds penetrate as well as grow in any organic matter on top of the fabric. Use of fabrics for ground cover plantings around trees may harm the tree, because tree roots will grow along the soil surface just under the fabric. The tree will suffer if these roots dry out. In the past, plastic films were placed under organic or mineral mulches to aid in weed control. This practice has fallen out of favor, since ground covers in such conditions grow poorly after several years.

Maintenance

A common mistake is to assume that ground covers are “maintenance free” and can be ignored after planting. Ground covers do not thrive on neglect any more than other plants. Maintenance can include: watering during dry periods, pruning to rejuvenate new growth, edging beds to keep ground covers within boundaries, weeding, and watching closely for disease and insect problems. Most disease and insect infestations are not serious enough to harm the health and appearance of ground covers. Natural enemies do a lot to keep problem pests from becoming too serious. Non-chemical controls can include pruning and removing pest-infested plant parts from the area, handpicking insects and diseased leaves and reducing fertilizing and watering regimes if excessive amounts of new succulent growth (disease and insect-prone tissues) are produced. If chemical controls become necessary, consult your county extension agent or garden center for approved practices. Always follow the labeled recommendations.

Most ground covers require at least two years to establish 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 will benefit from supplemental irrigation. Without additional water, plantings may thin out and give way to weeds. The lack of selective weed control chemicals can be a disadvantage with most ground covers other than grasses. Maintaining the cover as a dense stand is, therefore, of utmost importance to reduce or exclude weeds.

Remember that ground covers will not cure every problem, nor compete with every weed. They require some maintenance for their true beauty to develop. But regardless of a garden’s style, ground covers can reduce yard maintenance, enliven troublesome spaces, soften edges and promote visual flow.

Q: There are warts all over the undersides of my hackberry leaves. What is this and will it kill my tree?

A: This is called hackberry nipplegall. It is the result of a small insect called a hackberry nipplegall psyllid. These psyllids overwinter in protected areas as adults and lay eggs in early spring on the undersides of the new leaves. The young nymphs begin to feed and as they do, raised swellings are produced which ultimately turn into the "warts" or galls with the little insects inside. In late summer, adult psyllids emerge from these galls. This condition is pretty harmless to the health of the tree and the psyllids are a favorite of several bird species.

Q: I received two beautiful Amaryllis plants for Christmas-both with several huge blooms. I cut off the flowers when they were finished and then leaves came out. I've had them in a bright southwest window and have been watering them. The leaves look great and are about 18-25 inches long. Is it too late to get them to re-bloom for Christmas?

A: Ideally plants should be planted outdoors in May, but try it now! In a protected location with bright filtered light, dig a hole and plant pot and all with top at soil level. Use a water-soluble fertilizer (10-60-10) or similar, every two weeks. Continue watering to keep soil moist but never soggy. In mid-September bring the pots and bulbs indoors, cut leaves off 1" above top of bulb and place in a cool (50-60 degrees F cool temperature is important), dark location for six to eight weeks. DO NOT WATER.
In the last week of November, after this rest period, repot bulbs in fresh potting mix with top half of bulbs exposed. Water well and set in a sunny, (55-65 degrees F cool is again important) location. Don't water again until green growth appears. When stalks grow to six inches, begin to water the plants. If they fail to flower, just maintain them as foliage plants as you did this year, and start the process in May next year. Good Luck!

Q: Quite a few of the leaves on my honeylocust tree are kind of shrivelled with yellowish stipple-like spots on the leaves. Some leaves are even turning yellow. What is causing this?

A: This condition was likely caused in the spring by an insect called a honeylocust plant bug that feeds on tender new buds and leaves. Although there is only one genreation per year, which occurs in the spring, there can be significant damage and controls can greatly benefit the tree. Vigorous hosing of foliage can be effective as well as control from several insecticides, labelled for use on honeylocust plant bugs. Timing of application at the earliest emergence of insects-usually by mid-May-is necessary for maximum benefit. There are some other insects which can cause damage to honeylocusts. If you are unsure, bring a sample into the Larimer County Cooperative Extension office for identification.

If you are considering xeriscaping to conserve water, planning is the critical first step, whether you are starting fresh or starting over. Consider xeriscaping in place of narrow turf strips, hard-to-maintain corners and south or west exposures that use the most water.

If you have an automatic sprinkler system, check for proper coverage and make sure water is not being wasted on sidewalks, driveways and streets. If necessary, replace heads or add heads to achieve efficient coverage.

Even drought-tolerant plants require relatively frequent watering while establishing their root systems. With good soil preparation, most non-woody plants will need two seasons, while trees normally require one season per inch of trunk diameter.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  July 20, 2004