Stems up to 2 m. long, often suffruticose at base, occasionally thinner, thinly or occasionally densely pubescent with stiff yellowish or brownish hairs, like the petiole, leaf laminas, peduncles and calyces, very rarely glabrous.
Perennial forming several to many annual prostrate or, when still young, suberect stems from a large thick fusiform tuberous root.
Leaf lamina very variable in size and shape, usually oblong or elliptic, varying to ovate or linear 2–10 × 1–9 cm., entire with usually rounded, truncate or subcordate base, sometimes broadly cuneate or cordate, obtuse or mucronate, sometimes emarginate, acute or broadly rounded at the apex, with the margin ciliate to sometimes densely ciliate upper surface thinly covered with strigose usually yellowish hairs, lower surface as thinly as the upper or more densely so; petioles usually much shorter than the laminas but occasionally about as long.
Seeds glabrous, grey, finely punctate to smooth.
Corolla magenta, funnel-shaped 3·5–6 cm. long; midpetaline areas usually thinly covered with silky appressed hairs, rarely quite glabrous.
Fruits only rarely produced, subglobose, glabrous, dark brown abruptly apiculate and the apiculus crowned by the persistent style base, enclosed by the slightly accrescent and coriaceous sepals, 1–4-seeded.
Inflorescences 1-flowered, sometimes 2-flowered, rarely 3- or 4-flowered; peduncle terete, usually shorter than the leaves; bracteoles very variable but usually lanceolate, acute, hairy like the calyx, sometimes broadly oblong; pedicels usually very short, rarely exceeding 6 mm.
Sepals generally lanceolate to ovate-lanceolate, 15–22 mm. long, subequal (inner ones slightly wider) but more or less unequal in specimens with broader oblong or ovate sepals in which the inner ones are narrower; usually acute or acuminate with very acute tips, rarely subobtuse; outer ones more or less densely covered with usually stiff yellowish hairs.