Article

Plants You Can Walk On

These tough little ground covers can withstand the occasional trampling

Fine Gardening - Issue 152

Mulching the 3 acres of display and trial gardens at my perennial nursery was becoming expensive and time-consuming, so I decided to explore ground covers that would eventually eliminate the need for mulch. As I trialed numerous ground covers that complemented my perennials and shrubs, I became smitten with those plants that proved to be strong enough to tolerate foot traffic from people touring my gardens as well as trampling by pets. It became obvious which ones were tough enough to withstand the heat and humidity we experience each summer, remain evergreen, and display dainty flowers for months. Here are my absolute favorites.

For heavy-traffic areas

The toughest ground covers can take daily traffic, as long as it’s not too abusive

 

The toughest of the tough

Green carpet rupturewort

Herniaria glabra and cvs.

USDA Hardiness Zones: 5 to 9

Size: 1 to 2 inches tall and 10 to 18 inches wide

Conditions: Full sun to bright shade; moist, well-drained, average to poor, rocky soil; drought tolerant once established; avoid excess moisture

I often refer to green carpet rupturewort as my “tractor-trailer” plant because wayward vehicles sometimes make deep impressions in my garden, but the rupturewort doesn’t even turn yellow. The creeping stems of tiny, bright green leaves form an extremely dense green carpet. The summer-blooming flowers are inconspicuous, but the plant does self-sow. So even though the seedlings are easy to remove, it is best situated in an area where its self-sowing is an asset. It prefers not to be covered with leaves for long periods of time. A major advantage of rupturewort is that it does not “melt out” in our humid summer conditions the way that many creeping thymes (Thymus spp. and cvs., Zones 4–9) often do.

A dense mat that changes with the seasons

 

Dwarf creeping wire vine

Muehlenbeckia axillaris ‘Nana’

Zones: 6 to 10

Size: 1 to 2 inches tall and 8 to 12 inches wide

Conditions: Full sun to partial shade; well-drained soil; drought tolerant once established; can withstand heavy clay

I like to use creeping wire vine to provide a contrasting color between my stepping-stones. It has wiry stems and tiny, dark, glossy green leaves that turn bronze with heat or cold. This dwarf variety forms a denser mat than the species. Tiny green flowers in spring (photo, right) are followed in fall by small transparent white fruit with black seeds. Because it runs under­ground as well as along the surface, this plant works well for a dry, well-traveled path, but it will adapt to a garden setting. It can withstand a lot of foot traffic and is good for erosion control even though it is deciduous. Dried winter foliage may be cut to ground level, or you can simply allow new foliage to grow over it in spring.

 

A dusting of delicate flowers

 

White star creeper

Pratia angulata

Zones: 6 to 10

Size: 1 to 2 inches tall and 8 to 12 inches wide

Conditions: Full sun to partial shade; prefers moist, well-drained, average soil but tolerates wet or poor soils; drought tolerant once established

White star creeper has a multibranching habit, both above the ground and below, and its dense foliage quickly covers an area. It is blanketed with starry, pure white flowers that brighten up the garden for most of spring, followed by round, reddish purple berries that attract birds in fall. It eliminates weeds among larger plants, and it cascades beautifully over stones. The rabbits in my garden love to nibble on the foliage, which is fine with me because they help keep the foliage even lower, making the white stars shine more vividly. Deer don’t seem to bother it, and it springs right back after people walk on it, even if that happens several times a day.

For moderate-traffic areas

Try these plants for areas that get traffic once a day or so

Thrives in deep shade

 

Dwarf mondo grass

Ophiopogon japonicus ‘Nana’

Zones: 7 to 10

Size: 2 inches tall and 4 to 6 inches wide

Conditions: Partial to full shade; evenly moist to dry, average soil

When I have a heavily shaded situation and want a short, dark green ground cover, I turn to dwarf mondo grass. My dwarf weeping maple, for instance, creates a dry, dark area during the growing season that becomes uninteresting during winter; I have tried many ground covers, but dwarf mondo grass seems to be the only plant that doesn’t mind the lack of light while it waits to be exposed in winter. It is a bit slow to spread, which makes it terrific between pavers because its slow growth keeps it from covering the stones. It is, however, easy to transplant the rooted runners to fill in as desired, and it excels as a lawn substitute in small areas.

Less aggressive than other ajugas

 

‘Chocolate Chip’ ajuga

Ajuga reptans* ‘Chocolate Chip’

Zones: 3 to 9

Size: 3 to 4 inches tall and 1 foot wide

Conditions: Partial to full shade; evenly moist to dry, average soil

I look forward to ‘Chocolate Chip’ ajuga’s bountiful spikes of bluish purple flowers to provide a welcome show in my spring garden. The small, dark purplish green leaves create a ground cover that is not as aggressive as larger-leaved ajuga varieties. It should be deadheaded, however—either by hand or by mowing with a mower on a high setting—to keep it looking tidy and to prevent self-sowing. Deer and rabbits show no interest in feasting on this weaving ground cover. ‘Chocolate Chip’ quickly fills empty spaces around larger plants, providing year-round beauty in settings that do not receive a lot of sun.

 

Months of blooms in hot, sunny areas

 

White cup flower

Nierembergia repens

Zones: 7 to 10

Size: 2 to 3 inches tall and 8 to 12 inches wide

Conditions: Full sun to partial shade; moist, well-drained, average soil; drought tolerant once established

White cup flower’s lovely quarter-size blooms cover mats of deep green foliage for three to four months in summer when there aren’t many other ground covers blooming. Although the bloom count is higher when the plant is grown in intense sun, its white buttercup flowers brighten slightly shady areas, as well. The plant could be considered aggressive because it roots at all nodes, but it provides a dependable ground cover. The dense underground runners keep most weeds from growing, but the plant is low enough to carpet around plants that are taller or have heavy basal growth. I love using this easy-to-grow, tough workhorse in my white-themed garden because it unites the entire area in one sweep.

 

Tough and aromatic

 

‘Archer’s Gold’ creeping thyme

Thymus pulegioides ‘Archer’s Gold’

Zones: 5 to 9

Size: 3 to 4 inches tall and 8 to 12 inches wide

Conditions: Full sun to partial shade; moist, well-drained, average soil; drought tolerant once established

‘Archer’s Gold’ creeping thyme has it all: bright gold evergreen foliage; a wonderful lemon scent to enjoy as one crushes it underfoot; and nice lemon flavor for cooking. Drought tolerant and deer resistant, it is excellent for herb-garden walkways, around rose beds as a mulch substitute, or as a beautiful disease-free lawn alternative. I particularly appreciate that it does not brown out in Virginia’s heat and humidity, as many other thymes do. It is also suitable for use in containers as a soil cover. Its light lavender-pink blooms are a bonus in summer.

 

Highlight shade-loving plants all year long

 

Miniature golden sweet flag

Acorus gramineus ‘Minimus Aureus’

Zones: 5 to 9

Size: 3 to 5 inches tall and 6 to 12 inches wide

Conditions: Light to full shade but will tolerate full sun with extra moisture; evenly moist to wet, boggy soil

Miniature golden sweet flag is like sunshine in my shady garden. As I look out my kitchen window on a cold winter day, its dwarf fans of bright golden grassy leaves cheerfully accentuate the dark leaves of my hellebores (Helleborus spp. and cvs., Zones 4–9) and remind me that winter does not have to be bleak. This moisture-loving ground cover will grow in clay soil as well as sandy loam with normal moisture, and it will naturalize in bogs or at the water’s edge. I enjoy using it between stones in pathways, between wooden ties in my steps, and as a golden mat. While it is a slow grower, it makes up for it by being deer resistant.

 

For light-traffic areas

An occasional accidental step off a path won’t hurt these plants

Bring rare color to the shade

 

Mini Kenilworth ivy

Cymbalaria aequitriloba

Zones: 7 to 10

Size: Up to 1 inch tall and up to 8 inches wide

Conditions: Full sun to partial shade; moist to dry, well-drained, average soil

This little gem did not read its tag, which says that it is a “shade plant.” We planted it in an aboveground box that serves as one of our fairy gardens in intense, full sun. One year later, we realized that it had performed stoically and was blooming out of every crack in the wooden box. It crept into the other plants and made them appear to have lovely snapdragon-like lavender flowers in April, long before they actually bloomed. Because mini Kenilworth ivy is usually only ¼ to ½ inch tall, it didn’t harm any of its neighbors with its aggressive behavior. Its tiny scalloped leaves hold tight to any rock or crevice, and it is relatively evergreen in mild winters. This little bulldog is also great in the shade around my heucheras (Heuchera spp. and cvs., Zones 3–8) and hostas (Hosta spp. and cvs., Zones 3–9), but it doesn’t like to be covered with tree leaves all winter. Warning: Do not confuse Cymbalaria aequitriloba with its superaggressive cousin C. muralis, which is taller and larger leaved and quickly overtakes one’s garden.

 

An ever-changing carpet of color

 

‘Coral Carpet’ sedum

Sedum album ‘Coral Carpet’

Zones: 4 to 8

Size: 2 to 4 inches tall and 1 foot wide

Conditions: Full sun to light shade; moist to dry, well-drained, average to poor soil

The small, jellybean-like foliage of ‘Coral Carpet’ sedum is like a chameleon when grown in dry, poor soil. Its leaves emerge a salmon-coral color, mature to bright green, then turn reddish bronze in winter, in the heat of summer, or when its nutrition is limited. The creeping stems root at the nodes and quickly form a dense mat of foliage. Tiny clusters of white to pale pink flowers appear above the foliage in early summer. I love to fit this deer- and rabbit-resistant sedum into small crevices or between stepping-stones because each little piece that is planted or that falls onto soil will root if it receives adequate water. But don’t worry; it is easy to pull out if it appears where you don’t want it.


Quick tips for growing ground covers successfully

Leave room for planting between stepping-stones and pavers

When creating a paving-stone pathway, I suggest leaving a minimum of 2 inches between the stones for easier planting. Use a somewhat gritty, well-draining soil mix between the stones. If possible, set the stones or pavers approximately 1 to 2 inches above the soil level so that the ground cover does not quickly creep over and cover the stone. When a pathway has stepping-stones, people usually don’t walk on the plants; thus, plants that tolerate heavy foot traffic are not always required. Most important, don’t plant succulents where they will creep over a stepping-stone or walkway because they can become slippery when crushed underfoot.

Water them carefully to avoid runoff

If you are establishing new plants, especially ones grown in small pots, it is necessary to water them several times each week (if it does not rain). Once they have developed roots into the soil, they usually don’t need additional water. Where water is not easily accessible, I like to use ice cubes or frozen containers of water to provide moisture, essentially “slow-release” water. The plant receives all the water from the slow melting process, so runoff is prevented.

Mulch until plants begin to spread

It is important to use mulch when planting to suppress weeds and to maintain an even moisture level. Once the plants have filled in, mulching is generally unnecessary. Spacing on most of these plants is, to me, a matter of money and patience. The suggested spacing can easily be extended if you are not in a rush to achieve complete coverage. Most of the plants will quickly provide rooted pieces that can be transplanted into bare areas.


Sandy McDougle is the owner of Sandy’s Plants, a grower of rare and unusual perennials in Mechanicsville, Virginia.

Photos: courtesy of stepables.com; Michelle Gervais; and courtesy of sandysplants.com. Illustrations: Martha Garstang Hill

Sources

The following mail-order plant sellers offer the widest selection of the plants featured:

Arrowhead Alpines, Fowlerville, Mich.; 517-223-3581; arrowheadalpines.com

Joy Creek Nursery, Scappoose, Ore.; 503-543-7474; joycreek.com

Sandy’s Plants, Mechanicsville, Va.; 804-746-7092; sandysplants.com

Stepables, Salem, Ore.; 503-581-8915; stepables.com

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