Notul. Nat. Acad. Nat. Sci. Philadelphia 74: 5. 1941.
Herbs, perennial, 1–2 (–3.8) dm; from a woody caudex; with a taproot. Stems few to several, ± decumbent to erect or ascending, unbranched, sometimes with short, leafy axillary shoots, hairs erect to spreading, long, soft, eglandular, mixed with short-stipitate-glandular ones. Leaves green, linear, lanceolate to broadly lanceolate, oblong, or cuneate, 0.8–5 cm, not fleshy, margins plane to wavy, involute, 0–5-lobed, apex acute, sometimes rounded; lobes spreading, linear, arising below mid length, nearly as broad as center lobe, apex acute. Inflorescences 3–14 × 1.5–4.5 cm; bracts proximally greenish, rarely dull reddish purple, distally white to cream, rarely pale-yellow or dull, pale-pink (sharply differentiated from proximal coloration), lanceolate or oblong to narrowly ovate, (3–) 5–7-lobed; lobes ascending, linear to obovate, ± broadened distally, medium, long, proximal lobes arising below mid length, central lobe apex broadly rounded to truncate, others acute to rounded. Calyces colored as bracts, 15–26 mm; abaxial and adaxial clefts 3.5–7 mm, 25–50% of calyx length, deeper than laterals, lateral 2–5 mm, 12–25% of calyx length; lobes linear, oblong, or narrowly triangular, center lobe apex usually rounded, lobes acute to rounded. Corollas curved, 17–23 mm; tube 15–19 mm; beak exserted, adaxially green, 5–8 (–9) mm, puberulent, stipitate-glandular; abaxial lip deep purple (color sometimes visible through calyx), green, pinkish, or pale-yellow, ± prominent, slightly inflated, usually hidden in calyx, sometimes right at top of calyx, 2 mm, ca. 50% as long as beak; teeth ascending, whitish, yellowish, pink, or green, 1–1.5 mm. 2n = 48.
Phenology: Flowering Apr–Jul.
Habitat: Arid, rocky, sandy, or clay slopes of basaltic origin, sagebrush steppes.
Elevation: 400–800 m.
Castilleja xanthotricha is endemic to moderate elevations in the sagebrush hills of the John Day River drainage in north-central Oregon. N. H. Holmgren (1971) hypothesized that this tetraploid species is of allopolyploid hybrid origin between C. glandulifera and C. oresbia.
"acute" is not a number.