Perennial herb from woody rootstock; stems erect, to 75 cm long (rarely twining to 3 m), terete or quadrangular, glabrous or sparsely puberulous, usually with lines of hairs at nodes. Leaves slightly fleshy, palmately veined; petiole 1–4 cm long, glabrous or sparsely puberulous; lamina ovate to elliptic or slightly obovate, largest 8–17.5≈5.5–9.5 cm, apex acuminate to broadly rounded, apiculate, base attenuate to truncate, decurrent, margin entire or with a few large irregular teeth, glabrous (rarely sparsely puberulous). Flowers in many-flowered axillary racemes (rarely two racemes per axil or one raceme and a solitary flower); peduncle and axis 2.5–30 cm long, glabrous to finely puberulous; bracts caducous, lower foliaceous, upper bracteole-like; pedicels 0.8–3.5 cm long, puberulous; bracteoles pale green with conspicuous raised dark green reticulation, ovate to elliptic, 2–2.7≈0.8–1.2 cm, acute to obtuse, apiculate, puberulous. Calyx puberulous, 2–4 mm high of which the broadly triangular lobes about half. Corolla limb and upper part of tube purple to royal blue, lower part of tube tube whitish, throat yellow; tube (2.5–)3–4.5 cm long; lobes 1–1.5≈1.5–2 cm. Filaments 10–15 mm long, glabrous; anthers 2–3 mm long. Capsule 8–10 mm in diameter, beak 16–20 mm long. Seed pale brown, ± 7 mm in diameter with reticulate surface and strong lateral ridge.