Notul. Nat. Acad. Nat. Sci. Philadelphia 227: 2. 1950.
Herbs, perennial, 0.5–1.6 dm; from a woody caudex; with a taproot. Stems few to several, erect to ascending, decumbent at base, unbranched except for small, leafy axillary shoots, hairs weakly spreading to appressed, ± matted, especially distally on stem, fairly short and sparse proximally, longer and denser distally, soft, eglandular, becoming woolly, often obscuring surface. Leaves gray with hairs, surface green to purple, linear to narrowly lanceolate, 1–3.8 cm, not fleshy, margins plane, sometimes ± wavy, involute, 0–3-lobed, apex acute; lobes ascending-spreading, linear to narrowly lanceolate, apex acute to obtuse. Inflorescences 2.5–6 × 1–2.5 cm; bracts greenish to pale yellow-green or very pale, dull purplish throughout, lanceolate to oblong, (0–) 3 (–5) -lobed; lobes usually ascending, linear, medium length to long, arising near mid length, apex acute. Calyces yellow, color mostly obscured by whitish hairs, 15–22 mm; abaxial, adaxial, and lateral clefts (5.5–) 7–12 mm, 35–55% of calyx length, often appearing shorter because matted hairs stitch proximal part of clefts shut, all 4 clefts subequal; lobes broadly linear, apex acute. Corollas straight, 18–25 mm; tube 3.5–5.5 mm; subequal to calyx, or beak and sometimes abaxial lip exserted; beak adaxially yellow, 6–8 mm, hairs moderately long, matted on midline, very short-glandular on sides; abaxial lip green, inconspicuous, slightly pouched, 3.5–5.5 mm, 60–90% as long as beak; teeth erect, white or yellow, 0.5–3 mm. 2n = 24.
Phenology: Flowering Jun–Aug.
Habitat: Gravelly slopes and flats, turf and fellfields, mostly alpine.
Elevation: 1700–3600 m.
Castilleja nivea is endemic to alpine habitats in the mountains of northwestern Wyoming and adjacent Montana. It forms occasional hybrids with C. pulchella, which often shares its habitat, as on the Beartooth Plateau in northwestern Wyoming.
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