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Selecting Ground Covers

by Carl Brady

Add visual and textural interest

Liriope in the foreground as part of a larger composition. Photos by Carl Brady unless otherwise noted. Solidago sphacelata ‘Golden Fleece’ provides sprays of golden flowers from mid-August through September. An excellent ground cover and bee and butterfly charmer. Photo courtesy of North Creek Nurseries.

In garden spaces where trees, shrubs and larger perennials dominate, ground covers are often overlooked as key features of a composition. Not only do they obscure whatever lies beneath, but they can also be architectural elements that add visual appeal and textural interest to the landscape.

Old standbys

When many landscapers hear “ground cover,” they probably think of plants like Liriope (L. spicata or L. muscari), Pachysandra (P. terminalis), periwinkle (Vinca minor) and ivy (Hedera helix). For sure, those plants play a role in the landscape, and when they are planted as part of a well thought-out design, they can be fantastic, but there are many great options beyond those old standbys.

Grower suggestions

Wally Pressey, general manager of Classic Groundcovers in Athens, Ga., suggests using ferns as versatile plants with potentially four seasons of interest. While some ferns may be taller than what is often considered ground cover height, they can be grown to occupy large patches of a garden and act like a ground cover in that space.

“There’s a fern for every section of the country. When people want to have a landscape that’s sustainable and looks good from year to year, ferns are an important piece of that puzzle. The autumn fern (Dryopteris erythrosora) and the Christmas fern (Polystichum acrostichoides) both are hot because they are mostly evergreen, and when it’s the middle of January and everything else is bleak you can look outside and see that autumn fern still doing its thing, that’s exciting.”

Pressey also cites creeping raspberry (Rubus calynoides) and black mondo grass (Ophiopogon planiscapus ‘Arabicus’) as real attention grabbers, although for completely different reasons.

“The Rubus is like having a full-sun ivy. It spreads, it covers, it chokes out other things that might come up, whereas a lot of the ivies might not work in full sun. The black mondo is slow-slow to multiply and slow to spread, consequently, it is expensive, but the color draws a lot of attention and people want to talk about it.”

Richard Davis, president of The Ivy Farm in Locustville, Va., reminds us to look before we leap.

He says, “The most important thing before you get into the architectural end of it is making sure you’re getting the right plant for the right place. Site location and orientation is probably the most critical thing. From there, you can start looking at your architecture parts. Do you want more of a feathery foliage like a Liriope or Ophiopogon (mondo grass) or Carex (sedge), or do you want a broadleaf like Sarcococca (sweet box) or Pachysandra?”

Davis encourages landscapers to use more ivies as ground covers; after all, he lists 47 varieties in his catalog.

“There are so many varieties of ivies, don’t just be settled with one. There are some that can cover an area rapidly, and there are some that won’t cover it in years. Variegated ivies are slower growing, and a lot of time, the more diminutive the leaf is, the slower it grows. Ivies do well to about Zone 5 in hardiness and don’t like irrigated areas,” he says.

North Creek Nurseries in Southeastern Pennsylvania grows seven varieties of foamflower (Tiarella cordifolia), an early-blooming woodland native. Sales Manager Kevin Staso says, “Tiarellas are the ideal plant for that difficult spot that’s dry shade, underneath trees or around tree roots to fill in, places where it’s difficult getting other plants to grow.”

Iris cristata in foreground as part of a composition.

Staso also suggests using grass-like sedges (Carex spp.) for difficult places. Some will tolerate dry shade, others don’t mind wet feet. He says that a dwarf selection of the native goldenrod (Solidago sphacelata ‘Golden Fleece’), “is a wonderful ground cover for part-sun that forms a blanket of yellow, billowy 12-inch-tall flowers that bloom from late August to Thanksgiving.”

Rick Watson of The Perennial Farm in Glen Arm, Md., grows a large selection of ground covers. He says, “The one thing you’ve got to be careful of with some of these ground covers is that if they’re not aggressive enough, then weeds start coming up. You have to have ground covers that grow fast enough that they can compete with the weeds.”

For sunny, well-drained sites, Watson says blue-eyed grass (Sisyrinchium angustifolium) is a grassy, native plant that is a tough ground cover. Blue star creeper (Isotoma fluviatilis), “blooms like crazy, is tough as nails and can handle shade.” Also, Sedum (S. rupestre ‘Angelina’) “has a chartreuse color, it’s evergreen and brightens even the winter garden.”

Sweet woodruff (Galium odoratum) works well in the shade and has an excellent leaf texture and fragrance. Irish and Scottish moss (Sagina subulata and cultivars) do well in the shade and between stepping stones, as does Mazus (Mazus reptans), if it’s not too shady. Creeping thymes (Thymus spp.) are quick growers and smell good when you step on them.

Plants I like

My own favorite ground covers vary depending upon location and my mood. Often, I make choices because I want to contrast foliage with neighboring plants. For instance, if I already have a lot of spiky-leaved plants adjacent to a space, I’m unlikely to use Liriope. Instead, I’ll try a broadleaf plant, like dwarf sweetbox (Sarcococca hookeriana humilis). It’s a low-growing evergreen with inconspicuous flowers that effuses the garden with a fantastic scent in early spring.

Budget is frequently an overriding factor in determining what ground covers to use. Sweetbox and mondo grass are expensive plants. When dozens are needed to fill a given space, that cost is magnified.

Crested iris (Iris cristata) is a 6 to 10-inch-tall native that has wide little Iris leaves and beautiful flowers of blue and white in midspring, depending upon the cultivar. Plumbago (Ceratostigma plumbaginoides) is a great, 10-inch-tall, blue-flowering ground cover that provides color in the fall. A sterile variety of lamb’s ear (Stachys byzantina ‘Silver carpet’) has soft, fuzzy, gray leaves that people can’t resist touching and isn’t weedy like some other lamb’s ears. Oreganos (Origanum spp.) make excellent ground covers that may get a little weedy, but are fairly easy to control; many are good in the kitchen, too. There are many more excellent plants to use as ground covers, and the possibilities change by region.

Foamflowers, Tiarella cordifolia, are commonly found in the woods of eastern North America, but not nearly often enough in gardens. They are easy to grow and many will spread when given moist soil high in organic matter and shade. In the early spring fairy wand flowers of white or light pink appear. Photo courtesy of North Creek Nurseries.

Availability is extremely important. I can’t count how many times I’ve assumed that I’d be able to pick up a certain plant at a nursery and it’s not there when I need it. This problem is magnified when the plant I want isn’t carried everywhere. Also, finding some plants late in the season is difficult, and I find it necessary to compromise and choose alternate plants for a project.

When trying to get ideas for plants to consider for a landscape design, I leaf through my collection of catalogs from local and regional suppliers. They usually grow and stock plants that do well in my area, so I don’t have to worry about hardiness with my selections. I’ve learned a lot from looking through catalogs, too. Each spring, when I see plants listed that I’ve never used, I’ll buy one or two of each to plant in my yard so I can monitor them and see what they do. If I like them, I’ll start using them in clients’ yards. If they don’t work for me, I’ll give them to friends who are more than happy to take them off my hands. In this manner, I’m constantly expanding my plant palette.

I grow weary of seeing the same plants used too often in landscapes and planted without imagination. The next time you need a ground cover, I encourage you to broaden your search and try new plants. Experiment with different foliage types and play around with different combinations.

The author is a writer and landscape gardener in Silver Spring, Md.