Stems weak, prostrate to ascending, glabrous or minutely villosulous above; lvs palmately veined, the lower petioled, the upper sessile or nearly so; fls from the upper axils, on pedicels 1-4 cm; cal accrescent in fr, very irregular, the throat oblique, the upper median lobe broadly ovate and blunt (sometimes mucronate), the other 4 lobes very short or obsolete; cor bright yellow, sometimes with reddish-brown dots, the throat open, the lower lip bearded; 2n=28, 30, 60, 62, 90, 92. In shallow water or very wet places, especially in calcareous situations; Mich. to Man. and Mont., s. to S. Amer. June-Sept. Most of our plants belong to var. fremontii (Benth.) A. L. Grant, with entire or repand to irregularly denticulate, subrotund to ±reniform or occasionally rotund- ovate lvs, the cor mostly 8-15 mm; c. and n. Great Plains, e. to Ill., Mich., and Ont. Var. michiganensis (Pennell) Fassett, local near the Straits of Mackinac, Mich., has more ovate or oval, more obviously toothed lvs and mostly larger fls, the cor 15-25 mm; it may reflect ancient introgression from no. 5.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Rhizomatous perennial, rooting at nodes, glabrous or nearly so 10-60 cm tall. Leaves: Short petiolate below to sessile above, 1-3 cm long, palmately veined with 3-7 veins, the blade oblong to orbicular, dentate to entire margins. Flowers: Inflorescence of solitary flowers from the upper leaf axils, the pedicels exceeding the calyx, the calyx campanulate, 6-15 mm long, glabrous, lobes unequal, the teeth blunt, the corolla yellow and spotted inside, 1-2 cm long, early deciduous and bilabiate, the throat more or less open. Fruits: Loculicidal capsule in persistent papery calyx. Ecology: Found on moist to muddy soils, often submerged and along streams from 4,000-7,500 ft (1219-2286 m), flowers May-July. Distribution: Ranges north throughout the United States to Canada and south through Mexico to Central and South America. Notes: Distinguished by the corolla being entire or nearly so the calyx teeth never converging and the strongly bilabiate flower with the longer upper lip. Ethnobotany: The leaves can be eaten, as can the tender shoots. Etymology: Mimulus means ape-flower, or a diminutive of the Latin minimus, a comic or mimic actor, because of the grinning corolla, while glabratus means somewhat glabrous. Synonyms: None Editor: SBuckley, 2011