Castilleja plagiotoma
Castilleja hololeuca
Mojave desert paintbrush, Mojave Indian paintbrush, Mojave paintbrush
Channel Islands paintbrush, island paintbrush, island white-felted paintbrush, white-felted paintbrush
several, erect to weakly ascending, often leaning on nearby shrubs, much-branched, often with short, leafy axillary shoots, hairs sparse, spreading, short or long, soft, branched or unbranched, eglandular.
many, erect to spreading, much-branched with many short axillary shoots, proximal stems reaching 1+ cm wide, white-felted, hairs dense, spreading to ± appressed, intertwined, long, soft, slightly branched, obscuring surface.
gray-green or green to purple to ± deep red, linear or linear-lanceolate, 2–5 cm, not fleshy, margins plane to ± wavy, flat or involute, 3–5(–7)-lobed, apex acuminate to acute;
lobes spreading-ascending, sometimes widely so, narrowly linear, apex acute or obtuse.
ash gray, leaves of previous year persisting on proximal stem, linear, older leaves sometimes broadly linear, 1–5 cm, not fleshy, margins plane, involute, 0-lobed, apex obtuse;
lobes ascending, linear-lanceolate, apex obtuse to rounded, sometimes acute.
3–20 × 0.5–1.5 cm;
bracts green throughout, sometimes tinged dull purple, proximal sometimes linear-lanceolate, distal or all bracts oblong, 3–5(–7)-lobed;
lobes spreading to ascending, linear to oblanceolate, short to long, proximal lobes arising near mid length, sometimes wavy-margined, central lobe apex rounded to truncate, lateral ones obtuse to rounded.
3–16 × 2–4 cm;
bracts pale gray-green throughout, or proximally pale gray-green, distally red or yellow, proximal linear, distal broader, often oblanceolate to obovate, (0–)3-lobed;
lobes spreading, linear to oblong, short to long, arising below mid length, apex rounded to truncate or acute.
straight, 13–20 mm;
tube 5–7 mm;
beak short-exserted, sometimes shorter than abaxial calyx segments, adaxially yellow, rarely greenish, 7–10 mm;
abaxial lip pale green to yellowish, reduced, 0.5–1.5 mm, 7–17% as long as beak;
teeth reduced to apiculations, pale green to yellowish, 0.5–0.8 mm.
slightly curved in proximal 1/3, 14–26(–31) mm;
tube 9–17 mm;
abaxial lip not exserted, beak exserted;
beak adaxially green to yellowish, 11–14 mm;
abaxial lip ascending, deep green, reduced, 2–3 mm, less than 33% as long as beak;
teeth reduced to apiculations, deep green, 1–1.5 mm.
light green, cream, or light yellow, often appearing white from dense white-woolly pubescence, 10–18 mm;
abaxial clefts 5–6.5 mm, closed by intertwined hairs and appearing 2 mm deep, adaxial 2.2–4.2 mm, abaxial ca. 25% of calyx length, adaxial ca. 20% of calyx length, shallower (or appearing much shallower), than laterals, lateral 4.6–7.5 mm, ca. 50% of calyx length;
lobes: abaxial segments broad, paddle-shaped, 7 mm, inner surface of abaxial segments densely white-woolly, apex rounded to broadly obtuse, adaxial narrowly triangular, 5 mm, apex acute.
colored as bracts, with conspicuous whitish veins, 14–18(–20) mm;
abaxial and adaxial clefts 5–12 mm, 30–67% of calyx length, deeper than laterals, lateral 0 mm or nearly so, ca. 0% of calyx length;
lobes linear-lanceolate, apex rounded, truncate, or emarginate.
Castilleja plagiotoma
Castilleja hololeuca
Castilleja plagiotoma is unique in the genus in the structure of its calyces, with the lateral clefts deeper than the median clefts. The relative lengths of the calyx lobes are also unique, with the abaxial lobes exceeding the adaxial lobes by 2–3 mm. The abaxial lobes also bear a dense indument of whitish, branched hairs. The uniformly greenish bracts are uncommon among perennial species of Castilleja. Castilleja plagiotoma is scattered in the western Mojave Desert and the hills adjacent to the southwestern San Joaquin Valley, California. While not of immediate conservation concern, this species is uncommon and increasingly threatened by recreational vehicles, livestock grazing, residential development, and resource extraction.
Castilleja plagiotoma is most often associated with and is likely parasitic on Eriogonum fasciculatum var. polifolium, but it is also often observed with Artemisia tridentata or other species. It is a known larval host plant for the butterfly, Euphydryas editha subsp. erlichii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Castilleja hololeuca is endemic to the four major islands of the northern Channel Islands. It is similar to C. lanata, a mostly Mexican species that reaches Arizona, New Mexico, and southwest Texas. However, C. hololeuca appears to be more closely related to C. foliolosa, a species of the California mainland. These three species, and C. galehintoniae G. L. Nesom of Nuevo León, all share a distinctive, thick indument of pale, matted, and often branched hairs on the stems and leaves. Large individuals of C. hololeuca form thick, woody trunks. On Anacapa Island, closest to the mainland, red-flowered forms of C. hololeuca predominate. On Santa Cruz Island, to the west, both red- and yellow-bracted forms are fairly common, usually in separate populations. Further offshore, on San Miguel and Santa Rosa islands, most plants are yellow to, occasionally, peach in coloration. Reports of this species from Santa Barbara and Santa Catalina Islands are referable to other species, mostly C. foliolosa. Populations of C. hololeuca historically declined from grazing by introduced game and livestock species. The plants are recovering well, following removal of the grazing animals, and are now common in many areas, especially on San Miguel Island.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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