Syst. Bot. 16: 656. 1991.
Herbs, annual, 0.7–4.7 dm; with fibrous-roots. Stems solitary, erect, branched, sometimes unbranched, glabrous or glabrate proximally, pubescent distally, hairs moderately dense, spreading, short to long, soft, eglandular, often mixed with short-stipitate-glandular ones (except var. obispoënsis). Leaves pale green, linear to broadly lanceolate, linear-lanceolate, or ovate, 1.4–9 cm, not fleshy, margins plane, flat or slightly involute, (0–) 3–5-lobed, apex acuminate; lobes ascending, linear to narrowly to sometimes broadly lanceolate, apex acuminate to acute. Inflorescences 1–16 (–20) × 2.5–4 cm; bracts proximally greenish to deep purple, distally white, or pink to pink-purple or reddish purple on apices, if white sometimes aging pink, lanceolate, 3–5-lobed; lobes ascending, linear to oblanceolate, long, arising below mid length, apex acute to acuminate. Calyces colored as bracts, 5–20 mm; abaxial and adaxial clefts 4.7–15 mm, 33–90% of calyx length, slightly deeper than laterals or all 4 clefts subequal, lateral 3–8 mm, 33–60% of calyx length; lobes linear to narrowly oblanceolate, apex acute. Corollas straight, 14–29 mm; tube expanded distally; abaxial lip and beak exserted from or equal to calyx; beak straight, adaxially pink, purple, or white, if white often aging light pink, (4–) 5–7 mm, densely puberulent, hairs often stipitate-glandular; abaxial lip proximally white or pink to deep purple, expanded part white throughout, or proximally white or purple, or green becoming light pink with age, distally white or yellow (sometimes becoming orange with age), purple or maroon spots or blotches on each lobe, inflated, lobes 3, pouches gradually (to abruptly) widened, 4–6 mm wide, 2–3 mm deep, deeper than tall, 3–7 mm, 80–100% as long as beak; teeth erect, pink, white (often turning pink with age), chartreuse, or purple, sometimes with deep purple spot at base, 1–2.5 mm. Filaments glabrous. 2n = 24.
Calif., Mexico (Baja California)
Varieties 3 (3 in the flora).
Castilleja densiflora is often confused with C. exserta, and both species are broadly overlapping in both range and habitat, often occurring in close proximity. However, intermediates are remarkably rare. The two are most easily separated by the structure and pubescence of the corollas. In addition to the characters mentioned in the key, C. densiflora usually has a bilobed stigma that is exserted from the apex of the corolla with a more or less vertical orientation, while that of C. exserta emerges horizontally and is capitate. These differences are remarkably consistent.
|1||Bracts distally white, rarely pale yellow; coastal grasslands; San Luis Obispo County, sc California.||Castilleja densiflora var. obispoënsis|
|1||Bracts distally pink to pink-purple to red-purple, rarely white; near-coastal and interior grasslands; widespread in w California.||> 2|
|2||Abaxial lips of corollas appearing slightly inflated, pouches widening gradually, longer than deep, 3–7 mm; calyces 8–20 mm.||Castilleja densiflora var. densiflora|
|2||Abaxial lips of corollas appearing moderately inflated, pouches widening abruptly, deeper than long, 4–5 mm; calyces 5–11 mm.||Castilleja densiflora var. gracilis|
"acute" is not a number.