Phytoneuron 2012-39: 32. 2012.
Herbs, annual. Stems erect to ascending, 0–100 (–120) mm, glandular-puberulent and/or glandular-pubescent. Leaves usually cauline, relatively even-sized; petiole absent, larger with petiolelike extension; blade oblanceolate to elliptic, (4–) 8–32 (–37) × (1.5–) 2.5–14 (–18) mm, margins entire or crenate, plane, apex obtuse, surfaces glabrous or puberulent and/or pilose adaxially. Pedicels (1–) 2–5 mm in fruit, usually twisting to invert calyx. Flowers 2 per node, or 1 or 2 per node on 1 plant, chasmogamous or cleistogamous. Calyces distinctly asymmetrically attached to pedicel, inflated in fruit, 5–14 mm, sparsely pilose, lobes subequal, apex obtuse, ribs green to purplish, intercostal areas whitish. Corollas: throat whitish to dark magenta, not golden yellow at base, lobes magenta, without markings or with dark magenta dots and, sometimes, some yellow at bases of abaxial lobes, palate ridges absent or purple, tube-throat 8–30 mm, limb 3–9 mm diam., bilabiate, abaxial lobe usually smaller than adaxial. Anthers (distal pair) exserted, glabrous. Styles glandular-pubescent. Stigmas exserted, lobes unequal, abaxial 3–4 times adaxial. Capsules 4–8.5 mm, indehiscent. 2n = 18.
Phenology: Flowering Feb–May.
Habitat: Serpentine soils, periphery of granite outcrops, disturbed hillsides, soil from decomposed granite, near water runoff areas, away from seeps or other areas with prolonged surface moisture.
Elevation: 100–1100(–1700) m.
Diplacus congdonii occurs in the Sierra Nevada Foothills and mountain ranges along the coast.