General:
Perennial herb from a branching, woody stem-base and a fibrous root; stems numerous, 40-150 cm tall, usually branched, very finely hairy to glabrous, 4-angled.
Leaves:
Opposite, egg- to heart-shaped, 3-10 cm long, 1.5-7 cm wide, margins coarsely toothed, glabrous or slightly roughly short-hairy above, glabrous or very short hairy to roughly short-hairy below; stalks 1-5 cm long.
Flowers:
Inflorescence a terminal spike of unstalked flower clusters, 3-15 cm long; corollas tubular, rose-purple to whitish, 10-14 mm long, 2-lipped, lower broader and longer, upper 2-lobed; calyces usually tinged lavender-purple, 3-veined, teeth 3-5 mm long, narrowly triangular-pointed; stamens 4, exserted, in 2 pairs, one longer.
Fruits:
Nutlets, 4 clustered together, oblong, about 2 mm long, brown, small hairs at tip.