Erect perennial 20–80 cm high, with leafy stolons produced late in the season. Stems with sparse curved hairs in upper part and with raised lines decurrent from leaf bases. Leaves usually opposite, alternate in the flowering region, lanceolate to narrowly ovate, 1.5–10 cm long, often broad-based, with numerous regular shallow teeth. Flowers with a conspicuous long, dense, pubescent ring inside hypanthium and a close and partly glandular pubescence outside. Petals 3.5–6 mm long, purplish pink. Capsule 4–7 cm long, closely pubescent; pedicel 0.5–1.5 cm long. Seeds obovoid, 0.9–1 mm long, comose.