Shrubs, 10–30 dm. Stems branched, tomentulose. Leaves: stipules absent; petiole 1–5 mm; blade elliptic to ovate, 2–10 × 1–4 cm, base acute, margins entire or sinuate-dentate, apex acuminate, abaxial surface appressed-hairy, adaxial glabrate. Inflorescences terminal, pendent, tapering-spicate thyrses, 4–20 × 2–4 cm, cymes secund, 10–20 pairs, 1–5-flowered. Pedicels essentially absent; bracteoles absent or present. Flowers fragrant; calyx densely hairy externally, tube 1.5–3 mm, lobes 0.5–1 mm; corolla curved, purple with white throat, tubular, tube 11–14 mm, lobes suborbiculate, 2–3 × 2–3 mm; stamens inserted 3–5 mm distal to base of corolla tube, included in tube; ovary ovoid, 1.5–2.5 mm, glabrate; stigma clavate, 1–1.5 mm. Fruits capsules, brown, ellipsoid, 4–6 × 2–2.5 mm, glabrous or sparsely glandular, dehiscence primarily septicidal. Seeds tetrahedral, 0.7–1 × 0.5–0.7 mm, wings narrow at edges. 2n = 38.
Phenology: Flowering Jun–Oct; fruiting Aug–Nov.
Habitat: Roadsides, railroad embankments.
Elevation: 10–200 m.
Introduced; Ala., Ariz., Fla., Ga., La., Miss., N.C., S.C., Tex., Asia (China, Japan), introduced also in West Indies (Guadeloupe, Jamaica, Martinique).