North America is home to over two dozen species of clematis, but very few of these are found in gardens. Our native species lack the big, blowsy blooms of the garden hybrids, producing instead demure, understated flowers. To compare the two is to compare a raucous pop song with a gentle fiddle tune. Both are satisfying in their own way, and both have a place in the garden.
Most of our indigenous clematis are leather-flowers (Clematis subgenus Viorna), so called because four very thick sepals make up the showy part of the flower. These fattened sepals are fused together at least partway along their edges; the flowers are often described as vaselike. To me, the little blooms often look like pursed lips; it is hard to dispel.
All of the native leather-flower clematis discussed in this article are completely herbaceous, and you can cut them down to the ground in either fall or early spring. However, a few native clematis, known collectively as virgin's bowers, have woody perennial stems and must be pruned more carefully. The purple virgin's bowers, Clematis occidentalis (USDA Zones 3-8) and its close relative C. columbiana (Zones 4-8), bloom on old wood, or last year's growth, and should be pruned just after they flower. The largest-flowered of any of the native species, they bear two- to three-inch cupped violet blooms on three- to six-foot vining stems in spring. Both are somewhat challenging to grow. In the East we find the western C. columbiana easier than our local C. occidentalis. It succeeds in partial shade and moist, fertile soil. A compact, nonvining Rocky Mountain variety, C. columbiana var. tenuiloba, is absolutely breathtaking tumbling over a boulder in the rock garden.
White virgin's bowers make up for purple virgin's bowers' lack of vigor several times over. Clematis virginiana (Zones 3-8) and its western cousin C. ligusticifolia (Zones 4-8) are both very easy, almost weedy vines that will smother any support you plant them near, especially in partial to full sun and fertile soil.
Scarlet leather-flower (Clematis texensis) is the most famous native clematis, the only species with red flowers. All red hybrids have it in their background. This lovely vine hails from the Edwards Plateau of central Texas but can be easily cultivated as far north as USDA Zone 5. The blooms are about an inch long, with sepals that are either pinkish red or a true, vivid scarlet on the exterior and soft custard yellow on the interior. White-leaf leather-flower (C. glaucophylla; Zones 5-9), a similar species, occurs from Georgia west to Mississippi. Like its scarlet cousin, it has glaucous or blue-gray foliage. Its flowers are a pretty reddish pink. Vasevine (C. viorna; Zones 4-9), a common southeastern species, blooms paler pink. The sepals roll back along their edges, revealing more of the custard-colored interior and giving the blooms a two-toned appearance. These three species grow to about six feet and bloom on new wood. If given a good, moist soil and at least a half-day of sun, they will continue to grow and bloom from early summer to early autumn.
Among the purple leather-flower vines, I like bluebill and blue jasmine. Bluebill (C. pitcheri; Zones 4-9) grows wild from Texas to the Great Lakes, and over this wide swath the flowers vary in size and color. The exterior of the flower ranges from nearly gray to royal purple. In the best forms the interior is also deep violet, so when the long, artful sepal tips curve back they reveal a hint of royal velvet. Bluebill is one of the parents of the incredibly long-blooming hybrid 'Rooguchi', with its rich purple flowers. Blue jasmine (C. crispa; Zones 5-9) produces flowers that look frosted with silvery blue. Their tips roll back elegantly to showcase a ruffled and fluted interior. This species has very narrow leaves and flowers in one flush in late spring.
The nonvining leather-flowers are a favorite of mine. Species such as the delicate white-hair leather-flower (C. albicoma; Zones 4-9) from the Virginia mountains stands only eight inches high when in bloom. We grow it in our partially shaded rock garden. It forms thick clumps, and a single pale pink to soft yellow urn-shaped bloom crowns each stiff, leafy stem in late spring. During pollination, the heavy sepals fall away to reveal a tuft of hairy stamens. As the seeds ripen, these fuzzy stamens resemble a knot of pewter curlicues and remain quite pretty through the summer.
Similar bonus interest can be had from another clumping species. Curlyheads (C. ochroleuca; Zones 5-9), slightly larger in all respects than C. albicoma, has rather dull yellow-green flowers, but the tails of its seeds turn a remarkable lustrous gold. These twisted, golden heads stay effective for about two months in summer, before the seeds ripen and fall in August.
In the western mountains you can sometimes find a small clematis with deeply dissected leaves and dark purple flowers. Slow-growing and a bit challenging, sugarbowls (C. hirsutissima; Zones 3-8) nevertheless makes an irresistible addition to the sunny rock garden. Fremont's leather-flower (C. fremontii; Zones 4-9) hails from the wind-tossed plains of Kansas, Nebraska, and Missouri. I call it the Art Nouveau clematis, because its flowers have the slender proportions of a fine Lalique vase. It is also a bit slow-growing, but it thrives in average soil and sun. Finally, Addison's leather-flower (C. addisonii; Zones 5-9), a rare plant from the Appalachian foothills of Virginia, falls somewhere between a vine and a shrubby perennial. Its foliage is glaucous purple and its flowers, rich plum.