Mimulus alatus is a perennial herb from rhizomes, stems 0.2-1.3 m tall, 4-sided, hollow, winged at corners.
Leaves opposite, each pair at right angles to the next (decussate), stalk 1-2 cm, winged, blade 6-13 cm long, 3-5 cm wide, reduced upwards, lance-shaped, pointed at both ends, margin sharply toothed.
Flowers violet to pale lavender, yellow in throat, hairy, showy, 2-4 cm long, bilaterally symmetrical, tubular, 2-lipped, upper lip 2-lobed, lower lip 3-lobed, base arched to obscure entry of corolla tube (throat), tips rounded; stamens 4,in 2 pairs of unequal length (didynamous) shorter than corolla tube; style also short, stigmas 2, flattened; ovary superior, 2-parted; calyx 1-1.6 cm long, 5-ribbed, lobe tips sharply linear; flowers solitary in leaf axils on stalks shorter than calyx, 0.2-1 cm; blooms July-Sept; pollinated by insects (Yatskievych 2006).
Fruit becoming dry, a cylindrical capsule 1cm long, enclosed by old calyx; seeds numerous.
Wetland status: OBL.
Frequency in NYC: NYS Rare, watch list, S3 R.
Habitat: Open marshes, wet woods, stream banks; soil pH 6.2-7.8; tolerant of shade, anaerobic soil; intolerant of drought, fire, salt.
Notes: Eaten by grazing animals (USDA, NRCS 2006).