General: annual and fibrous-rooted, or perennial by stout stolons, often rooting at nodes, very variable in stature and vigor, sometimes dwarf and small-leaved, sometimes robust and nearly a meter high, but usually 10-50 cm tall.
Leaves: opposite, 1-5 cm long, irregularly toothed, hairy or hairless, ovate to rounded or reniform to cordate, palmately or sub-palmately veined, the 3-7 main veins all arising at or near the base. Lower leaves stalked, the upper becoming stalkless, those among the flowers reduced, relatively broad, tending to clasp the stem, and sometimes joined at bases.
Flowers: few to several in top clusters, or sometimes solitary in small forms, long-stalked. Calyx enlarging after flowering, irregular, the upper tooth much the largest. Corolla yellow, 2-4 cm long, averaging longer than the flower stalks, strongly 2-lipped, and with flaring throat, dotted or more heavily marked with maroon on or about the well-developed, hairy palate.
Fruits: capsules, broadly oblong, 1-2 cm long, contained in inflated 'balloons' of fused sepals.
In wet places, from the plains to moderate elevations in the mountains, in w. and c. parts of MT. Also in the Rocky Mts. from AK and Yukon to n. Mexico.
The leaves of yellow monkeyflower were eaten, raw or cooked, by native peoples and early settlers in the Rocky Mountains. They have a slightly bitter flavor, and were mostly added to salads. The leaves were also used as a lettuce substitute and as a salt substitute.
The plant has agents that cause tissue to contract, and was used for healing wounds, fresh cuts, etc., usually used as a poultice. A decoction of the leaves and stems was used by the Kawaiisu as a herbal steam bath for chest and back soreness. The Shoshoni used a poultice of the crushed leaves applied to wounds, rope burns etc. The plant is used in Bach flower remedies - the keywords for prescribing it are 'Fear or anxiety of a known origin'.
The commoner forms are more or less robust, mostly 20-80 cm tall, and often stolon-producing, with the leaves well developed (sometimes as much as 8 cm long) and with the mostly several or many flowers rather large, the corolla 2-4 cm long. These represent the var. guttatus. More or less stunted forms, seldom over 30 cm tall, generally without stolons, and with the leaves 0.5-2 cm long and the often fewer flowers only 1-2 cm long, tend to occur in less distinctly wet habitats than var. guttatus, and sometimes bloom very early in the spring. These have been segregated as var. depauperatus (Gray) Grant.