Amer. J. Sci. Arts, ser. 2, 34: 251. 1862.
Leaves strictly annual, disintegrating in 1st year; blade ovate to slightly cordate, sometimes oblong, 25+ mm wide, leathery, base cuneate, truncate, cordate, or lobate, margins crenate, teeth apices acute, surfaces glabrous or sparsely hairy; basal veins extending into distal 1/2 of blade, lateral veins 3–6 on each side of midvein. Racemes erect, to 10 cm in fruit; sterile bracts 5–14, ovate-spatulate, largest 1+ cm; flowers 100+, densely aggregated (separating in fruit). Sepals 4. Petals (3 or)4(or 5), apex entire or erose; corolla blue, bluish purple, lavender, or reddish, bilabiate, ± rudimentary, tubular, longer than calyx, glabrous, lateral and abaxial petals of abaxial lip connate 1/2+ their lengths, tube absent. Stamens inserted on receptacle. Ovaries: ovules 17–40. Capsules glabrous.
Phenology: Flowering May–Aug; fruiting Jun–Sep.
Habitat: Stony alpine meadows or fellfields.
Elevation: 2800–4300 m.
Colo., N.Mex., Utah, Wyo.
Synthyris alpina is a host plant for checkerspot butterfly (Euphydryas anicia), which consumes leaves and sequesters iridoid glycosides (K. M. L’Empereur and F. R. Stermitz 1990). Flowering in plants of S. alpina begins at the margins of melting snow banks.