Herbs, perennial, 1–3(–4) dm; from a stout, woody caudex; with a taproot. Stems several, erect or ascending, unbranched, sometimes branched, hairs sparse, spreading or retrorse, moderately long, soft, crisped, eglandular, mixed with shorter ones. Leaves green, brown, or purple, linear to lanceolate, 1.5–6 cm, not fleshy, margins plane, rarely ± wavy, involute, 3–5(–7)-lobed, apex acuminate to acute; lobes widely spreading, deep, linear to narrowly lanceolate, lateral lobes not much narrower than central one, apex acuminate. Inflorescences 3–22 (longer in fruit) × 1–5 cm; bracts proximally greenish to deep purplish, distally bright red or scarlet, sometimes orange to pale yellow, linear, (3–)5–7-lobed, sometimes with secondary lobes; lobes spreading, linear to oblanceolate, long, arising below mid length, apex acute to obtuse. Calyces colored as bracts, sometimes paler proximally, 15–26(–33) mm; abaxial clefts 4–7.4 mm, adaxial 7–10 mm, abaxial 21–37% of calyx length, adaxial 28–51% of calyx length, deeper than laterals, lateral 1.5–3.5(–5) mm, 8–18% of calyx length; lobes lanceolate to triangular, apex acute. Corollas straight, 20–35 mm; tube 13–23 mm; beak and usually part of abaxial lip exserted; beak adaxially green, 6.9–13 mm; abaxial lip deep green, reduced, thickened, included or visible through front calyx cleft, 1.7–3.8 mm, 10–25% as long as beak; teeth incurved, yellow or deep green, 0.7–1.7 mm. 2n = 48.
Phenology: Flowering Jun–Aug.
Habitat: Rocky slopes, ledges, talus, ridges, open conifer forests, moist to dry substrates, montane to alpine.
Elevation: 1200–3100 m.
Castilleja covilleana is endemic to the mountains of central Idaho and adjacent southwestern Montana. A collection of unusually tall plants was described as C. multisecta. Castilleja covilleana is closely related to C. rupicola.