Syst. Bot. 16: 657. 1991
Herbs, annual, 0.5–4 dm; with fibrous roots. Stems solitary, erect, unbranched or branched, hairs spreading, long, soft, scattered among more numerous, medium length, stipitate-glandular ones. Leaves green or purplish, linear to narrowly lanceolate, 1–5 cm, not fleshy, margins plane, flat, 0–5(–7)-lobed, apex acuminate; lobes spreading to ascending, linear, apex acuminate to acute. Inflorescences (1.5–)3–14 × 2–3 cm; bracts green throughout, sometimes proximally green, distally white on apices, lanceolate to ovate, 3–7-lobed; lobes spreading to ascending, linear to narrowly lanceolate, long, arising below mid length, apex obtuse to acute. Calyces light green, lobes green, 7–13 mm; abaxial and adaxial clefts 3.5–8 mm, 50–67% of calyx length, lateral 2.5–5 mm, ca. 40% of calyx length; lobes narrowly to broadly lanceolate, apex acute to acuminate. Corollas straight, 10–22 mm; tube 8–15 mm; abaxial lip and beak exserted; beak adaxially yellow to greenish, 3–6 mm, densely puberulent; abaxial lip yellow with purple dots at base, inflated, pouches 3, central pouch slightly 2-lobed, pouches 4–8 mm wide, 3–6 mm deep, side pouches curving up a little at tip, 2–5 mm, 75–95% as long as beak; teeth erect, white or yellow, 0.5–2 mm. Stigmas equal to or slightly exserted from beak. 2n = 22, 24.
Phenology: Flowering (Mar–)Apr–Jul(–Aug).
Habitat: Grasslands, meadows, moist flats, vernal pool margins, moist forest openings, serpentine slopes and ledges, roadsides.
Elevation: 0–2700 m.
Castilleja lacera is found in a wide range of elevations in the central and northern Sierra Nevada region and in the Siskiyou Mountains region of northwestern California and southwestern Oregon. Reports from the Coast Ranges north of the San Francisco Bay region and south of the Siskiyou region in western California are referable to other yellow-flowered annuals, including C. ambigua, C. rubicundula var. lithospermoides, Triphysaria eriantha subsp. eriantha, and T. versicolor subsp. faucibarbata. Although most similar to C. rubicundula, C. lacera is somewhat smaller in stature and flower size. It is also easily confused with yellow-flowered populations of C. tenuis, which has smaller flowers and an included stigma. Two chromosome numbers are known for this species, the more northern populations being diploid, and those to the south having an apparently aneuploid count of 2n = 22, which is unique in the genus.