Justicia americana is a perennial herb, colonial from rhizomes, stems 50-100 cm tall, mostly unbranched, rooting at lower nodes.
Leaves opposite, 8-16 cm long, 0.8-2.5 cm wide, linear to lance-shaped, pointed at both ends.
Flowers pale violet to white with purple markings on lower lip, bilaterally symmetrical, tubular, about 1 cm long, 2- lipped, lips about as long as tube, asymmetric, lower lip 3-lobed; inflorescence of crowded in head-like clusters 1-3 cm long, on stalks 5-15 cm long; blooms June-Aug.
Fruit a dry capsule, seeds 0.3 cm, rough.
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Muddy soil, pH 5.4-7.6, shallow water of rivers and lakes, shade tolerant (USDA, NRCS 2006).