Stems viny, to 4 m, without cobwebby pubescence, nearly glabrous, or moderately pilose-pubescent proximal to nodes. Leaf blade mostly 1-pinnate, some simple; leaflets usually 4-8 plus additional tendril-like terminal leaflet, lanceolate to ovate, unlobed or 2-3-lobed, or most proximal 3-foliolate, 2-12 × 1-5(-6) cm, thin, not conspicuously reticulate; surfaces abaxially sparsely to densely pilose, not glaucous. Inflorescences axillary, 1-7-flowered; bracts well above base of peduncle/pedicel. Flowers broadly urn-shaped to bell-shaped; sepals pale lavender to reddish purple, grading to cream-yellow toward tip, ovate-lanceolate, 1.5-3 cm, margins not expanded, very thick, not crispate, tomentose, tips acuminate, recurved, abaxially sparsely to densely pubescent. Achenes: bodies silky-pubescent; beak 2.5-6 cm, plumose. 2 n = 16. Flowering spring-summer. Wooded cliffs and stream banks; 0-1400 m; Ala., Ark., Del., D.C., Ga., Ill., Ind., Ky., Md., Miss., Mo., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va. The Fox Indians prepared a drink from the roots of Clematis viorna to use medicinally as a panacea (D. E. Moerman 1986).
Stem climbing, generally somewhat hairy at least at the nodes; principal lvs with 2-4 pairs of lfls, some of the lfls often trifoliolate; lfls lanceolate to ovate, entire or 2-3-lobed, thin, not prominently veined, generally hairy beneath and at the rachis-joints, not glaucous; cal urceolate; sep ovate or lance-ovate, 1.5-2.5 cm, caudate-acuminate, thinly hairy on the back, densely tomentose at the margins; style at anthesis hirsute, at maturity 3-5 cm, densely plumose throughout; 2n=16. Moist woods and thickets; Pa. to Ill. and Mo., s. to Ga. and Miss. (C. gattingeri; Viorna viorna; V. flaccida, a more hairy form)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.