Shrub or subshrub, up to 4 m tall; stems glabrous to tomentose. Leaves opposite or in whorls of 3–4; blades narrowly elliptic or oblanceolate to ovate or obovate, 1.5–15 x 0.5–9 cm, acute to acuminate at the apex, cuneate at the base, entire to serrate, glabrous to tomentose; petiole 0–25 mm long. Flowers in ± leafy cymes that are sometimes arranged in short-pedunculate panicles. Calyx cup-shaped, glabrous to tomentose; tube c. 5 mm long; lobes rounded to triangular, 1.2–3(–5) mm long, glandular inside. Corolla with midlobe dark blue or violet blue, lateral lobes pale blue or mauve; tube 5–7 mm long, inflated in front and with a deep slit at the back; lobes unequal, the midlobe largest. Fruit 5–6 x 8–10 mm, mostly deeply 4-lobed.