Annual or rarely perennial herb or undershrub 0.15–1 m. tall; stems slender, erect or rarely procumbent, much-branched, covered with dense white scaly hairs above but glabrescent below or rarely ± glabrous. Leaves opposite or appearing verticillate owing to the presence of very abbreviated axillary shoots; blades lanceolate to linear-lanceolate, 1–7.5 cm. long, 0.2–1(–2) cm. wide, acute at the apex, cuneate at the base, somewhat revolute at the margins, glabrous to densely covered with adpressed scaly white hairs particularly above; petioles almost or quite obsolete; stipules with 3–4 fimbriae ± 1.5–3 mm. long. Flowers geminate in terminal spikes 1.2–15 cm. long (up to 26.5 cm. in fruit); pedicels obsolete. Calyx-tube ovoid, 1 mm. long, densely covered with spreading bristly hairs; lobes 5, 1 foliaceous, lanceolate, 3–5 mm. long, 1–2 mm. wide, with entire revolute margins usually covered with white bristly hairs, rest of lobes small or minute, unequal, densely hairy. Corolla white or usually red, lilac, mauve or blue; buds with limb abruptly expanded into an ovoid head; corolla-tube very narrowly filiform, (2–)3.5–6 mm. long, 0.2 mm. wide, glabrous; throat glabrous; lobes 4–5, lanceolate, 2–2.5 mm. long, 0.5–0.75 mm. broad, usually hairy outside. Stamens 4–5, exserted for up to ± 2 mm.; filaments glabrous. Style filiform, the stigma bilobed, lobes filiform, 1–1.5 mm. long, style and stigma together exserted for a distance equalling the corolla-lobes. Fruit pale yellow-brown to dark purplish brown, ovoid, 2 mm. long, 1.2–1.5 mm. wide, densely covered with white hairs. Seeds black, ovoid, 1.4 mm. long, 0.9 mm. wide, ventrally flattened, granulated, slightly keeled dorsally and with a narrow depression surrounding the hilum.
