Herb 0.2–0.4(–1) m high; branches scabrous, erect or ascending from a creeping rhizome. Leaves sessile, rigid, oblong-ovate or narrowly obovate, 4–12 cm long, 1–4 cm wide, glabrous, apex acuminate, base subcordate and partly clasping branch, margin coarsely and sharply serrate, often slightly revolute. Inflorescence a lax terminal corymb with long branches ending in a dense spike. Bracts conspicuously longer than calyx. Calyx 5-toothed, 4–6 mm long, glandular-pubescent or hirsute; corolla reddish-purple, pale lilac or blue-violet, 2–3 times as long as calyx, tube 8–10 mm long. Mericarps c. 2 mm long. Flowers throughout the year.
VVP, VRiv, MuF, GipP, OtP, CVU, EGL, EGU, HSF, VAlp. Also naturalised WA, SA, Qld, NSW. Native to South America. A weed of moist ground, apparently uncommon in Victoria, recorded from the Yarra River between Warrandyte and Warburton, and Eildon Reservoir.
