Low perennial herb from a creeping rhizome, sometimes also with stolons; stems erect to decumbent at the base, 5-20 cm tall, sometimes branched, smooth or sparsely hairy.
Opposite, short-stalked to unstalked, elliptic to egg- or diamond-shaped, the blades 5-25 mm long, irregularly few-toothed, palmately 3- to 5-veined from the base; leaves not much reduced upward.
Inflorescence of 1 to 3 (5) long-stalked flowers in the axils of the upper leaves, the stalks 1-6 cm long; corollas tubular, broadly funnel-shaped, yellow with maroon markings in the flaring throat, 2-4 cm long, strongly 2-lipped, the lips spreading, the upper lip 2-lobed, the lower 3-lobed, yellow-hairy at the throat; calyces bell-shaped, pale yellow-green with reddish spots, smooth to minutely hairy, 7-15 mm long in flower, to 20 mm and asymmetrically swollen in fruit, 5-toothed, hairy in the notches between the teeth, the upper tooth larger than the others; stamens 4.
Capsules, oblong to oval, rounded at the tip, 5-10 mm long; seeds numerous, about 0.5 mm long.
Synonyms and Alternate Names:
Mimulus tilingii var. caespitosus (Greene) A.L. Grant
Erythranthe caespitosa Regel
Mimulus implexus Greene
Mimulus luteus var. alpinus A. Gray
Mimulus scouleri var. caespitosus Greene