Phytoneuron 2012-39: 29. 2012.
Herbs, annual. Stems erect, 10–180 (–230) mm, densely glandular-pubescent and viscid. Leaves basal and cauline, basal in rosette, cauline gradually reduced distally; petiole absent; blade obovate to narrowly elliptic, 3–46 (–70) × 1–20 (–25) mm, margins entire or crenate, plane, apex rounded or obtuse, surfaces: proximals glabrate, distals glandular-pubescent and viscid. Pedicels 1–3 (–6) mm in fruit. Flowers 1 per node, chasmogamous. Calyces symmetrically attached to pedicels, inflated in fruit, 5–10 mm, glandular-pubescent and viscid, lobes subequal, apex obtuse, often apiculate, ribs dark green to purplish, intercostal areas whitish. Corollas pink to magenta, throat floor with 3 dark purple lines meeting abaxial lip lobes, palate ridges yellow, tube-throat 7–10 mm, limb 4–7 mm diam., not bilabiate. Anthers nearly exserted, glabrous. Styles eglandular-puberulent. Stigmas nearly exserted, lobes unequal, abaxial 5–7 times adaxial. Capsules 7–11 (–12) mm. 2n = 16.
Phenology: Flowering Apr–Jul.
Habitat: Recently burned or cleared areas, sandhills, sandstone outcrops, sandy gravel and loam, decomposed granite, serpentine-derived soils, open chaparral, chaparral margins, open yellow pine-manzanita woodlands.
Elevation: 300–1300 m.
Diplacus rattanii occurs mostly in near-coastal localities from Glenn and Lake counties south to Ventura County.