Soft herb, often sprawling, sometimes erect; branches often tinged purple, glabrous or hairy. Leaves narrowly ovate, 1.2–6 cm long, 0.8–2 cm wide, glabrous or shortly hispid (particularly on lower surface), apex acute, margin with 4–14 serrations; petiole 0–5 mm long. Flowers in dense 3–12-flowered clusters in axils of distal leaves; pedicels much shorter than calyx. Calyx 3–5 mm long, 13-veined, densely covered with short spreading hairs, lobes up to c. as long as tube; corolla white or pink, exceeding calyx by 1–3 mm, lobes c. 1–2 mm long, the posterior one emarginate; anthers shortly exserted. Flowers Feb.–Oct.