Proc. Acad. Nat. Sci. Philadelphia 73: 532. 1922.
Herbs, perennial, 1.5–3.5 dm; from a slender, woody caudex; with a taproot or stout, branched roots. Stems few-to-many, erect to ascending, unbranched or branched, hairs appressed to ± ascending, matted, long, soft, mixed with short-glandular ones, denser distally, sometimes obscuring surface. Leaves green, sometimes brown, linear to linear-lanceolate, 3–7 cm, not fleshy, margins plane, involute, 3–7-lobed, apex acute to rounded; lateral lobes spreading, narrowly linear, apex acuminate. Inflorescences (3.5–) 8–20 × 2–5.5 cm; bracts proximally greenish, distally bright-yellow, sometimes pale-yellow to pale orange, sometimes aging white to pink, narrowly to broadly lanceolate or oblong, 3–5 (–7) -lobed; lobes spreading to ascending, linear, long, arising at or below mid length, apex obtuse to rounded. Calyces green, pale green, or whitish, lobes colored as bracts, 12–18 mm; abaxial and adaxial clefts 8–15 mm, 60–75% of calyx length, deeper than laterals, lateral 2.5–3 mm, 20% of calyx length; lobes linear to very narrowly triangular (equilaterally triangular if very short), apex obtuse to rounded. Corollas straight but curved at tip, 30–41 mm; tube 21–26 mm; beak slightly to long-exserted, adaxially green to yellowish, sometimes aging pinkish, 10–15 mm; abaxial lip white or yellow, sometimes partly green, darkening with age, only slightly inflated, exserted from abaxial cleft, 3–7 mm, ca. 50% as long as beak; teeth prominent, petaloid, spreading, yellow, 2.5–6 mm. 2n = 24.
Phenology: Flowering (Mar–)Apr–May.
Habitat: Calcareous prairies, sandy fields, gravelly limestone hillsides, limestone outcrops, mesquite, juniper, oak-juniper, and post oak woodlands, roadsides.
Elevation: 300–800 m.
Kans., Okla., Tex.
Although the range of Castilleja citrina overlaps the range of its close relatives, C. lindheimeri and C. purpurea, in central Texas, C. citrina extends considerably farther to the west and northwest of the others (G. L. Nesom and J. M. Egger 2014). The inflorescences of C. citrina are mostly pale to bright lemon yellow or occasionally brassy yellow. The color and usually more elongate abaxial corolla lip separate it from C. lindheimeri and C. purpurea. Castilleja citrina is similar to some color forms of C. sessiliflora, but the more conspicuously curved corolla of C. sessiliflora is usually exserted far above the calyx and is often white to pale pink, rather than yellow.