Mem. New York Bot. Gard. 1: 359. 1900.
Herbs, perennial, 1.4–6 dm; from a woody caudex; with a taproot. Stems few to several, erect or ascending, sometimes decumbent at base, unbranched or branched, hairs spreading to retrorse, short, scabrid below inflorescence, sometimes becoming medium length to long, soft to stiff, mixed with short-stipitate-glandular ones in inflorescence. Leaves green, sometimes purplish, linear to lanceolate or narrowly oblong, 1–8.5 cm, not fleshy, margins plane, flat or involute lengthwise, 0 (–5) -lobed, apex acute; lobes ascending, linear, central one sometimes shallowly toothed, apex acute to obtuse. Inflorescences 3–14 × 1.5–3 cm; bracts greenish throughout, or proximally greenish, distally pale to bright-yellow or whitish, rarely pale orangish, lanceolate to oblong, (0–) 3–7-lobed; lobes ascending to erect, linear to lanceolate or narrowly oblong, medium length, arising at or above mid length, central lobe apex obtuse to rounded, lateral ones acute. Calyces colored as bracts, 15–25 mm; abaxial and adaxial clefts 6–13 mm, 50% of calyx length, deeper than laterals, lateral 1–7 mm, 15% of calyx length; lobes narrowly triangular to linear, apex acute. Corollas straight or slightly curved, 21–27 mm; tube 14–16 mm; beak partly exserted, adaxially green, 7–12 mm; abaxial lip ascending, green, reduced, 2–4 mm, 25–50% as long as beak; teeth erect or incurved, sometimes spreading, green or white, 0.7–2.5 mm. 2n = 48, 96.
Phenology: Flowering May–Aug.
Habitat: Grasslands, open conifer forests, moist meadows, rocky slopes, valleys, montane.
Elevation: 600–1900 m.
Alta., B.C., Idaho, Mont., Oreg., Wash.
Castilleja lutescens is found east of the Cascade Range in Oregon and Washington and ranges east to western Montana and the adjacent interior of western Canada. Its inflorescences vary in color from entirely greenish to white or yellowish, and the stature of the plants is also variable, trending from moderate and compact in grasslands to taller in more forested situations. In the Blue Mountains of Garfield County, Washington, occasional hybrids form between C. lutescens and C. hispida var. acuta, which often both occur in the same vicinity.
L. R. Heckard (1968) reported a chromosome count of ca. 2n = 120 from a population in Montana.
"medium" is not a number.