Woody vines (erect, herbaceous perennials in C. recta). Leaf blade 1-2-pinnate; leaflets lobed or unlobed, margins entire or toothed. Inflorescences terminal and/or axillary on current year's stems, cymes or panicles or flowers solitary or paired, bracteate. Flowers bisexual, or unisexual with staminate and pistillate on different plants, not nodding, or ± nodding in yellow-flowered species; perianth rotate; sepals spreading, not connivent, linear, oblong, elliptic, lanceolate, ovate, oblanceolate, or obovate, thin and white or somewhat thickened and yellow; filaments filiform, slender, glabrous or pubescent; staminodes absent from staminate flowers, usually present in pistillate flowers; pistils rudimentary or absent in staminate flowers. Achenes flattened or nearly terete; beak more than 1.5 cm, plumose.


Species 50-100 (11 in the flora).

The Asian (Korean) species Clematis serratifolia Rehder, with light yellow sepals and purple stamens, may also escape from cultivation and spread locally.


1 Sepals greenish yellow to bright yellow, ascending or wide-spreading and recurved. > 2
1 Sepals white to cream, wide-spreading, not recurved. > 3
2 Leaflet margins entire or coarsely few-toothed; sepals greenish yellow, pubescent or abaxially glabrous. Clematis orientalis
2 Leaflet margins serrate; sepals bright yellow, adaxially glabrous. Clematis tangutica var. tangutica
3 Flowers bisexual. > 4
3 Flowers unisexual. > 6
4 Stems herbaceous, not viny. Clematis recta
4 Stems ±woody, climbing with tendril-like petioles and rachises of compound leaves. > 5
5 Pistils 10 or fewer per flower; achenes flattened, with conspicuous rims. Clematis terniflora
5 Pistils 20 or more per flower; achenes nearly terete, without conspicuous rims. Clematis vitalba
6 Leaflets deltate to ovate, strongly 3-parted to 3-sect, segments ovate, deltate, or linear; achene with beak 4–9 cm; sw United States, Mexico. Clematis drummondii
6 Leaflets ovate to lanceolate, variously lobed or toothed, but without narrow segments; achene with beak to 5.5 cm. > 7
7 Flowers solitary (rarely 3 in simple cymes); pedicel (or peduncle and pedicel combined for solitary flowers) stout, 3.5 cm or more; pistils 75–100 per flower. Clematis lasiantha
7 Flowers (1–)3 or more, in simple or compound cymes or in panicles, occasionally solitary in C.pauciflora; pedicel slender, less than 3.5 cm; pistils fewer than 70 per flower. > 8
8 Achene body broadly ovate to nearly orbiculate, glabrous; sepals hairy only abaxially; leaflets to 3.5 cm. Clematis pauciflora
8 Achene body ovate, pubescent; sepals hairy on both surfaces; leaflets usually longer than 3 cm. > 9
9 Leaf blade 3-foliolate. Clematis virginiana
9 Leaf blade pinnately 5-foliolate to 2-pinnate. > 10
10 Inflorescences compound cymes, often distinctly corymbiform, flowers crowded; pistils 25–65 per flower; leaf blade somewhat succulent, ultimate venation obscure; w North America. Clematis ligusticifolia
10 Inflorescences panicles, not usually corymbiform or with flowers crowded; pistils 18–35 per flower; leaf blade membranous, ultimate venation conspicuous; primarily e North America. Clematis catesbyana