Bull. Torrey Bot. Club 17: 37. 1890.
Herbs, perennial, 0.7–2 dm; from a woody caudex; with a taproot. Stems few-to-many, spreading to ascending, unbranched except for short, leafy shoots in axils of leaves, glabrate to distally puberulent, hairs sparse to dense, spreading, ± short, soft, sometimes stipitate-glandular. Leaves green to purple, linear or narrowly lanceolate to narrowly oblong, (1.1–) 2–8 cm, not fleshy, margins plane, involute, (0–) 3–7 (–9) -lobed, apex acute to obtuse; lobes spreading, linear to narrowly lanceolate, apex acuminate. Inflorescences 2.5–5.5 × 1.5–2.5 cm; bracts rose-purple, magenta, lilac, or crimson throughout, or proximally greenish to dull purplish, distally as above, lanceolate to ovate or broadly elliptic, 3–7 (–13) -lobed; lobes spreading to erect, linear to narrowly lanceolate, long or short, proximal arising below mid length, central lobe apex rounded to acute, lateral ones acute. Calyces colored as bracts, 12–26 mm; abaxial and adaxial clefts 5–10 mm, 50% of calyx length, deeper than laterals, lateral 0.2–6 mm, 25% of calyx length; lobes triangular, apex acute. Corollas straight or slightly curved, 20–25 mm; tube 13–15 mm; beak exserted, sometimes part of abaxial lip equal to or exceeding calyx; beak adaxially green, 6–8 mm; abaxial lip greenish at base, becoming white to rose-pink on apices, reduced, slightly pouched, 2–3 mm, 33–50% as long as beak; teeth ascending, white, pink, or green, 1–2.2 mm. 2n = 24.
Phenology: Flowering Jul–Sep.
Habitat: Rocky slopes, meadows, fellfields, alpine.
Elevation: 3200–4300 m.
Colo., N.Mex., Utah.
Castilleja haydenii is endemic to high-elevation slopes in the Rocky Mountains of southern Colorado and northern New Mexico. It is known in Utah from a single collection from high elevations in the La Sal Mountains. Reports of this species elsewhere are usually attributable to C. rhexiifolia. Its affinities are uncertain. Some features are shared with C. rhexiifolia, but in other ways it resembles species such as C. lemmonii of the Sierra Nevada. Plants in the northwestern portions of its range tend to have less divided leaves. Castilleja haydenii occasionally hybridizes with C. occidentalis where the two commingle in the lower alpine zone.