- To +1m tall, erect, from fibrous roots, also producing rhizomes, glabrous, hollow, multiple from base or single, simple to sparsely branching, winged on opposing sides of stem, 4-angled.
- Opposite, sessile, clasping(sometimes narrowed to base and not clasping), auriculate, lanceolate to narrowly oblong, glabrous, serrate, acute, to 10cm long, +2cm broad. Auricles rounded.
- Single pedicillate flowers from leaf axils. Pedicels to 3cm long, glabrous.
- Corolla purple with yellowish center, to +2.5cm long, bilabiate. Corolla tube 1.8cm long, glandular pubescent above, white at base. Upper lip of corolla smaller and erect, 2-lobed, 1cm broad, 8mm tall, glandular pubescent externally. Lower lip larger, spreading, 3-lobed. Lateral lobes 1.5cm broad. Central lobe 1.1cm broad, with a bearded yellow "palate" that blocks the throat of the corolla tube. Stamens 4, didynamous, included. Filaments white, glabrous, adnate at middle of corolla tube. Anthers 2mm broad. Style 1.3cm long, white, glabrous. Stigma flattened, suborbicular. Ovary superior, green, glabrous, conic, 5mm long, 2mm in diameter, 2-locular. Placentation axile. Ovules many. Calyx tubular, to +1.5cm long, 5-angled, glabrous. Lobes linear-attenuate, scabrous on margins. Fruit an ovoid capsule to +/-1cm long, glabrous.
- June - September.
- Streambanks, lake margins, wet meadows. Often growing partially submerged.
- Native to U.S.
- This plant is very easy to identify in the wild due to its distinct flower, square stems, and choice of habitat. It is common in the wild and is even working its way into cultivation along with other species of the genus.
Steyermark splits the species into two varieties. Variety
has leaves which clasp the stem. A second variety, variety
, has leaves which taper to the base and do not clasp. Both are common.
Photographs taken in Ellington, MO., 7-13-03.