Herb 0.6–2 m high; branches erect, conspicuously quadrangular, slightly scabrous.
Leaves sessile, narrowly oblong-ovate, 4–22 cm long, 0.6–7 cm wide, rugose, scabrous and slightly villous above, tomentose below; base subcordate and partly clasping branch; margin coarsely incised-serrate; apex acuminate.
Inflorescence a lax terminal corymb with long branches ending in a dense spike; bracts equal to or shorter than calyx; peduncle and bracts strongly glandular. Calyx 5-toothed, 2.5–3.5 mm long, glandular-pubescent, hispidulous along ribs. Corolla blue, dark violet-purple or lavender-pink, scarely 2 times as long as calyx; tube 3.5–5 mm long.
Mericarps 1.5–1.8 mm long.