Herbs, annual, acaulescent or caulescent. Stems erect or ascending, 10–140(–170) mm, densely glandular-puberulent. Leaves basal densely clustered; petiole absent; blade narrowly elliptic to oblanceolate, (5–)8–45(–60) × (1–)3–12(–20) mm, margins entire, sometimes toothed, plane, not ciliate, apex obtuse, surfaces glandular-puberulent. Pedicels 1–3(–5) mm in fruit. Flowers 1 per node, chasmogamous. Calyces slightly asymmetrically attached to pedicel, not inflated in fruit, (6–)11–23 mm, densely glandular-puberulent, lobes subequal, apex obtuse, ribs often purplish proximally, intercostal areas whitish. Corollas tricolored, limb and throat magenta to purple, each lobe with a discrete, dark maroon-purple blotch at base, all 3 blotches of abaxial lip round and not usually extending into throat, palate ridges yellow, flanked with white, sometimes purple-spotted, tube-throat (13–)15–50 mm, limb 7–21 mm diam., bilabiate, lobes equal. Anthers included, with apical tufts of short, eglandular hairs. Styles usually glandular-puberulent. Stigmas nearly exserted, lobes subequal. Capsules (2–)3–8(–10) mm, indehiscent. 2n = 18.
Phenology: Flowering Mar–Jul(–Aug).
Habitat: Vernally flooded depressions in grasslands, low spots and ditches in and around agricultural fields.
Elevation: 50–1500 m.
Diplacus tricolor occurs in northwestern and south-central Oregon and from there across a disjunction to central California as far as Kern County.