Mimulus ringens is a perennial herb, 20-130 cm tall, (much like M. alatus but leaves stalkless, stems scarcely winged); colonial from rhizomes, stems hollow, sharply 4-sided, angles narrowly winged.
Leaves opposite, decussate, stalkless (sessile), blade 6-13 cm long, 2-3 cm wide, lance-shaped, progressively reduced above, tip pointed, base often clasping stem, margin toothed.
Flowers blue-violet, yellow in throat, hairy, showy, 2-3 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, tube sharply 5-ribbed, lobes are sharply pointed tips of ribs; flowers solitary in leaf axils on stalks longer than calyx, 2-4.5 cm; blooms July-Sept.; pollinated by insects (Yatskievych 2006).
Fruit becoming dry, a flattened, 2-parted cylindric capsule 1cm long (Radford et al. 1968), base enclosed by old calyx; capsule splitting open along each side to release numerous small seeds (Levine 1995).
Wetland status: OBL.
Frequency in NYC: Infrequent.
Habitat: Open wet areas, swamp forest gaps, stream banks, edges.
Notes: Winter plant opposite, upcurved branches, flower stalks appearing as small, opposite, upcurving branches, each pair at right angles to the next (decussate), each tipped by a calyx remnant; old calyx fragile, often ragged, strongly ribbed, concealing dry fruit capsule (Brown 1976; Levine 1995).