Under Cover: Ground Covers

There are various ways to cover soil and add dimension to a landscape, whether doing so by using turf, gravel, hardscapes, mulch or landscape plantings. However, making sure vibrant and layered color is seen throughout the seasons is becoming more of a trend in landscape design, pointed out Chris Miracle, landscape architect, LaRosa Landscape, Mequon, Wis. This means traditional ground covers aren’t always the solution for a majority of the landscape.

Because of this trend, low, dense-growing ornamental ground covers are becoming more popular. They provide an interesting landscape texture and help contractors solve functional challenges on properties, such as excessively shady areas, steep slopes and unusually small sites. The right ground cover can even satisfy a client’s need for a low-maintenance landscape.

"From a design standpoint, ground covers are nice alternatives to turf or excessively mulched areas," Miracle said. "While ground covers require a fair amount of nurturing in the first one or two years after planting, they are low maintenance in the long run and work well under trees or as overplantings for bulbs. They also provide a fair amount of weed control."

After a few years of adequate growth, however, the spreading nature of some ground covers can be considered invasive. Certain ground covers also can require perfect site conditions, ongoing fertility and winter protection to grow, which means they aren’t ideal for some clients.

PLANT PICKS. Many people refer to ground covers as a type of plant, but by definition a ground cover is actually the use of a particular plant, pointed out Anthony Woodyard, director of academic development, Horticopia, Purcellville, Va. "Most any plant, depending on how it grows, can be used as a ground cover," Woodyard said. "For example, in most contexts, I wouldn’t classify a daylily as a ground cover, but used en masse it can work very effectively."

Ground covers with rhizomatous or stoloniferous qualities, meaning their roots spread and propogate quickly, are useful in areas where soil is compact and plants won’t grow, Woodyard said.

Ground covers can be used in landscapes solely for aesthetic reasons, such as adding layers, color and texture to a design. "Ground covers add a living floor to an outdoor room," explained Kurt Kluznik, president, Yardmaster, Painesville, Ohio. "Many bloom, such as periwinkle (evergreen ground cover plants with blue flowers), Ajuga (a plant that has square stems and blue, white or rose flowers), sweet woodruff (a low-growing perennial herb with small, white flowers), Liriope (evergreen perennial ground covers with grass-like leaves and spikes of white or lilac-blue flowers) and fragrant honeysuckle. Many ground covers have attractive foliage, like the glossy green leaves of ivy, wintercreeper and periwinkle. Others have colorful foliage like the variegated leaves on Hosta and St.-John’s-wort. Cotoneaster has a weeping effect and prostrate junipers offer a mass of fine needles in various shades of greens and blues."

FUNCTION FACTORS. Ground covers are useful in small backyard gardens left with nominal turf space. "You wouldn’t want to mow back there," Miracle said.

Many contractors also install ground covers around large trees to protection them from mower damage, Woodyard added. "Instead of mowing turf right up to the trunk of the tree and possibly damaging its root system, ground covers can offer defense by keeping equipment away from the tree."

Ornamental ground covers also can prevent erosion along stream banks and slopes because the leafy plant greens slow water down instantly and tend to have deep root systems to keep soil stable. Crown vetch is one example of a functional ground cover, Kluznik offered. The plant, which has leaves that divide into many oval leaflets and lavender-pink flower clusters, is too invasive for cultivated areas, but excellent on banks and slopes where erosion control is important, Kluznik said. "Crown vetch roots can go 10 feet deep and thrive in soil conditions unsuitable for anything else," he said.

Turf won’t thrive in excessively shady, wet or dry areas, remarked Bruce Hoskins, owner Tokar’s Nursery, Canby, Ore. Yet ground covers can flourish in these areas.

But Hoskins warned that not all ground covers are perfect in every situation. "Pachysandra – four or five species of hardy evergreen shrubs – is widely used as a ground cover in shady situations or areas that get a little morning sun," Hoskins explained. "But in afternoon sun or areas that get all-day sun, Pachysandra will turn yellow, not green. Plant ivy, persistant Vinca and St.-John’s-wort in areas that get all-day sunshine instead."

For thirsty areas, drought-tolerant ground covers, such as succulents and junipers – durable plants that thrive in many soil varieties – work well, Woodyard remarked.

INSTALLATION INSIGHTS. Even though some ground covers will grow in compact or chemically imbalanced soil, preparation is still critical for proper growth. "Poor soil preparation can turn an intended maintenance problem-solver into a major maintenance headache and an eyesore," Kluznik commented. "Don’t save money on the soil preparation. Use a non-selective herbicide and preemergents to control weeds."

Then, the soil should be tilled to a 9- to 12-inch depth. "Drainage issues should also be dealt with prior to installation," Miracle said. "If you are trying to evenly blanket an area with ground covers, and drainage problems exist in different variations of the terrain, you could end up with inconsistencies."

However, when planting ground covers on a slope, "working up the soil is not practical," Hoskins said. "You should dig up your planting holes and plant your ground covers in pockets to avoid erosion problems."

Due to the potential for erosion on slopes, even invasive ground covers, which are recommended on steep hills, may need the help of a fiber mat to get rooted.

When planting, contractors shouldn’t "skimp on plant spacing," Kluznik said. "The goal is to create a dense monolithic appearance. Excessive gaps can fill with weeds if plants aren’t spaced close enough together. Contractors should select plants that have a fighting chance of growing – peat pots are better than rooted cuttings, quarts are better than peat pots and gallons are even better yet. Size does matter in this instance, but be prepared to pay for big-sizing."

To compensate in an area of compact soil, Woodyard said ground covers can be spaced closer together because they won’t get the same degree of growth.

COST CONCERNS. Ground cover installation can cost anywhere from 5 to 20 times more compared to turf costs, according to Kluznik. The reasons for this wide range of cost are that different ground covers cost more than others, and the square footage of the space being planted must be considered because more plants are needed if they are being used to fill an area.

"The cost of ground covers is a function of the area and type of material being used," Woodyard confirmed. "Ornamental ground covers may not be the best choice price-wise compared to turf or other plants, but they may still be the best option. This is where you have to know your plants. Planting 1,000 square feet of an extravagant ground cover wouldn’t be cost effective – it might be more cost effective to plant junipers instead. But for a small area, you may be able to plant the extravagant ground cover."The spreading tendency of the plant also should be taken into consideration when figuring the cost of a job, Woodyard said. "Putting in a large area of spreading juniper may not be cost effective, but filling the same area with English ivy may be cost effective because fewer plants are needed to fill the area," he explained.

But when maintenance is factored in, Kluznik said ground covers can be less expensive in the long run, even though their installation is more expensive.

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MAINTENANCE MATTERS. Even though ground covers are low-maintenance after they are established, they do require attention when initially planted. Watering needs of ground covers should be based on the type of plant installed. "For instance, a good, deep soaking every other day is important for Pachysandra," Miracle said. "Shrub materials or low-growing evergreens may only need two to three waterings a week if the soil they are planted in is thick. If contractors are planting small plants out of flats, they need to water more frequently. You have to be cautious, however, not to overwater spreading junipers or certain shrubs."

Ground covers also require thorough removal of leaves or trash during the spring clean-up process. "Ground covers planted under trees, especially, will get covered up with leaves," Woodyard said. "The leaves must be raked and removed. Also, a lot of ground covers become catch-alls for trash – this also needs to be cleaned out regularly."

Woodyard said ground covers also might require regular pruning once they are established because they get dense. "You generally want to prune without removing a tremendous amount of growth," he said. "Prune once each year and remove the maximum one year’s growth from the plant. Light pruning is better than hard pruning."

Miracle also suggested applying an annual dose of slow-release fertilizer to ground covers. Just as ground covers planted at the correct spacing eventually can choke out weeds, the opposite also can occur. "Weeds are a challenge to control in ground covers and the chemical solutions can be limiting," Kluznik explained. "Weeds or unwanted grasses can outperform new or struggling ground covers and sometimes the only solution is radical – that is bring in the napalm and start over."