Lianas , twining, to 25 m, woody. Young stem ribbed, tomentose. Leaves: petiole 1-5.5 cm. Leaf blade ovate to reniform, 9-20 × 8-15 cm, base cordate, sinus depth 1-2 cm, apex obtuse to acute; surfaces abaxially tomentose; venation palmate-pinnate. Inflorescences on new growth, axillary, solitary flowers; peduncle not bracteolate, 1-7 cm. Flowers: calyx yellow-green, sharply bent; utricle pendent, globose to cylindric, 0.5-1 × 0.5-0.8 cm; syrinx absent; tube bent, cylindric, 1-3 × 0.5 cm; annulus rugulose; limb yellow, 3-lobed, lobes triangular, 2 × 2 cm, glabrous; gynostemium 3-lobed, globose, 3 mm; anthers 6; ovary 6-locular, 1-7 cm. Capsule ellipsoid to cylindric, 6-8 × 4-6 cm, dehiscence basipetal; valves 3; septa entire, not attached to valves. Seeds flat, triangular, 1 × 1 cm. 2 n = 28.
"High-climbing woody twiner; lvs broadly round-cordate, 1–2 dm long and wide, softly hairy beneath, peduncles axillary, solitary or paired, 2–4 cm, densely tomentose, bractless; perianth bent, 4 cm, densely tomentose, nearly closed at the throat, the limb dark madder-purple, spreading to reflexed, subequally 3-lobed; fr cylindric, 6–8 cm; 2n=28. Wet, alluvial woods; s. Ind. to se. Kans., s. to Ga., nw. Fla., and Tex.; locally intr. in Mass. June."