Leaves strictly annual, disintegrating in 1st year; blade broadly elliptic to lanceolate, 25+ mm wide, leathery, base truncate to tapered, margins crenate, teeth apices acute to rounded, surfaces hairy; basal veins extending through proximal 1/2 of blade, lateral veins 5–12 on each side of midvein. Racemes erect, to 40 cm in fruit; sterile bracts 10–40, ovate-spatulate, largest 1+ cm; flowers 100+, densely aggregated (separating in fruit). Sepals 4. Petals 3(or 4), apex entire or erose; corolla yellow, bilabiate, ellipsoid, longer than calyx, puberulent on margins, lateral and abaxial petals of abaxial lip connate 1/2+ their lengths, abaxial and adaxial petal lips basally adnate to stamens, tube absent. Stamens inserted on receptacle, but abaxial and adaxial petal lips basally adnate to stamens. Ovaries glabrous or sparsely hairy at apex; ovules 17–40. Capsules glabrous.
Phenology: Flowering May–Aug; fruiting Jun–Oct.
Habitat: Moist subalpine or alpine meadows.
Elevation: 2100–3800 m.
Synthyris ritteriana is known from the San Juan and La Plata mountains, and adjacent areas of Gunnison and Montrose counties on San Juan and Hansen tuffs.