Groundcovers

The word groundcover has unpleasant connotations for many gardeners, bringing to mind seas of boring pachysandra or myrtle and suggesting even a certain lack of seriousness about gardening itself. But groundcovers play important roles, from dressing the bare ground beneath trees and shrubs to providing a backdrop for all manner of leggy bulbs and lanky perennials. Edgings of groundcovers can help tie paths into a woodland garden, and, of course, groundcovers worthy of the name, such as pachysandra and vinca, once established, eliminate many maintenance problems practically forever. But pachysandra and vinca are not one’s only choices. The native American flora is rich with other plants that also suppress weeds, require no deadheading, staking, or division, and need nothing more than natural rainfall and reasonably fertile soils to flourish. Many are also plants of the first distinction, admired worldwide for their elegance and beauty.

OUT OF APPALACHIA

Within the group of native plants suitable for groundcover, my favorite is actually a pachysandra. It is not, however, the one usually seen, Pachysandra terminalis, which is a native of Japan. Rather, it is a congener of that plant–the term botanists apply to any plants that share a genetic heritage but developed in parallel yet different ways after the continents split apart. Popularly called Allegheny spurge, from its natural range, its botanical name is Pachysandra procumbens, an odd misdescription, for its habit is not at all lax but, rather, stiffly upright. Its matte, mid-green leaves are produced in neat, flattened, four-inch-wide whorls atop naked stems as much as a foot tall. In an established patch, each whorl overlaps its neighbors to create a dense cover impenetrable j to weeds. Like so many native groundcovers, Allegheny spurge grows best in shade, even quite deep shade, but, sad to say, not dry shade, for it : craves the deep, moist, and humus-rich forest litter to which it is native.; It increases very slowly, with new shoots rising near existing ones and over time–sometimes a long time–creating a large colony. But as with all desirable plants that increase slowly on their own, a modest stock can best be built up by teasing the clump apart in early spring and planting the bits at more widely spaced intervals. Allegheny spurge is worth the effort.

Growing in almost the same natural range as Pachysandra procumbens is Shortia galacifolia, though it is a rarer plant, both in gardens and in the wild. Its common name, oconee bells, comes from a Cherokee word meaning “beside the waters.” That is where you are apt to find it, growing in moist shade near streams and on the shaded banks of woodland lakes. The plant shingles over the soil in an evergreen mass scarcely six inches tall. Its paddle-shaped leaves are rich green, heavily; veined, and so shiny, both above and below, that they seem varnished. With the advent of cold weather the foliage takes on beautiful tints of russet and bronze. And in spring, just as the snow melts, tiny snow-white bells emerge from burgundy calyxes. They last hardly a week, but during that week you should hope for visitors from England, where this plant is a holy grail. Your horticultural reputation will be assured.

The prettiest flowers shouldn’t, perhaps, last a long time, but leaves are a different matter. And so another American plant, again found in the rich woodland duff of the southeastern mountains, has always been celebrated for its leaves. They have the extraordinary capability of lasting up to three months in a vase of water. The plant is Galax urceolata, but since it is the only species in its genus, most people call it simply galax, or by its pretty common name, wandflower. A first cousin to shortia (which borrows its own species name galacifolia from it), it is so similar in leaf as sometimes to seem the same plant. But the galax is taller, to about 10 inches, and the leaves are slightly cupped, which intensifies their varnished elegance. Flowers, which occur briefly in early spring, are amazingly dainty little bottle brushes born high above the leaves, on stems so hairlike that they dance in the slightest breeze. The leaves, which at their largest measure not more than four inches each, turn a beautiful burnished red in autumn, when they used to be picked and dispersed in huge numbers by the florist trade. In fact, the city of Galax, Virginia, was once the center for such export, though since gathering plants from the wild has become appropriately unpopular, the town has turned to other pursuits.

LOW-GROWING SHRUBS

The plants so far discussed are herbaceous perennials, all producing lush leaves from crowns or stolons. But the North American flora also boasts several low woody shrubs that can form large colonies in the wild, and so can serve as useful groundcovers in the garden. The absolute aristocrat of that group must be Cornus canadensis, which bears the inelegant common name bunchberry, from the thick clusters of seed it forms in autumn. It is otherwise indistinguishable in everything but height from its aristocratic cousin, C.florida, the American dogwood. The leaves are the same, though borne in whorls atop stems hardly four inches tall. In the center, sometime in mid-spring, the “flowers” appear, really four chalk-white pointed bracts surrounding a cluster of tiny true flowers in the center. Because they are bracts, not petals, they hold on and look fresh for a long time. Outside its native habitats, which extend roughly from Nova Scotia to Virginia, C. canadensis can be cranky to get going. Keep in mind that its questing pink stolons travel best in well-decomposed leaf mold, or even in rotted bark mulch. If young plants are established in such nutrient-rich organic material, they may clamber across it gleefully, never looking back.

Among my favorites within this group of woody or semi-woody subshrubs is Paxistima. Of the two species grown in gardens, P. canbyi is the nicer, with tiny, needlelike, shiny green and finely toothed leaves borne alternately on sprays of wiry stems, but thickly enough to discourage all weed competition. It is popularly called by a pretty name, cliff green, attesting to the facts that it prefers moist but well-drained sites and is happiest growing at the top of a retaining wall or in a rock-strewn woodland. Its other popular name, rat stripper, is a little harder to understand, though I once did see plants in a garden stripped bare of every leaf, leaving only the naked brown twigs. Rats must have done that work, though I cannot think why. Paxistima has several ways of covering ground, for it forms stolons from the mother plant, but also roots wherever its lax stems touch moist earth. Flowers are not much– greenish white, summer-borne, and most people never see them, though presumably they set seed, and spread that way too.

Scandinavians might object to the claim that another wiry little shrub is “a native American,” for Vaccinium vitis-idaea van minus is their much loved lingonberry, first cousin to our cranberry, V. macrocarpon, both members of the magnificent blueberry clan. But lingonberries are in fact circumpolar, occurring just about everywhere cool and moist on the globe. They form dense mats of tiny, boxwoodlike leaves on wiry brown stems, spreading over the earth by means of stolons and stem tips and rooting as they go. This is an adaptable little plant, as comfortable growing in USDA Zone 2, where winter temperatures reach a low of -50′ F, as in Zone 7, where they dip only as low as zero. I do not know how the Scandinavians gather so many berries that they can put them up in jars and use them to glaze their superb roast chickens in winter. In my own garden, I often see their lovely nodding white bells in spring, and an occasional red berry at Christmas; but it would be a poor chicken indeed that would be glazed by any lingonberries I could gather. Still, the plant is very pretty, and on a sunny hillside slope here, it has flourished without care for years.

A WEST COAST STAR

All of these lovely plants are native to the eastern seaboard of North America, ranging from the White Mountains of New Hampshire, where vacciniums and Cornus canadensis flourish, down to the Virginias, where sheets of galax may be found. But the West Coast offers treasures, too, the best of which perhaps is Vancouveria hexandra, named for the British explorer George Vancouver, and not Vancouver, British Columbia, as is usually assumed. A native of Washington State down to the redwood forests of California, it has proven–as many West Coast natives do–surprisingly adaptable to other climates throughout zones 4 to 8. Wherever it grows, if it can be given cool shade and moist soil, it will form thick sheets of thumb-sized bright green leaves arranged on wiry stems fern-fashion, much like the florist’s maidenhair fern (Adiantum tenerum). It is a first cousin (another congener) of the beautiful Asian epimediums, but it grows lower than any of them, hardly ever reaching more than six inches in height. There are gardeners who have complained that it is rampant, and needs controlling every year by spading the outsides of the colony to sever the questing stolons. I wish you to be that lucky.

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