Orobanche uniflora subsp. occidentalis
Contr. Dudley Herb. 5: 99. 1958.
Plants simple or few-branched basally, sometimes also forked medially, (including pedicels) 3.5–18(–20) cm, stems and inflorescence axes only 1–5(–7) cm. Leaves and bracts usually 1–5 per stem or branch. Pedicels (8–)20–110(–140) mm. Calyx lobes subulate-triangular, 5–15 mm, ca. 2 times as long as tube, tapered abruptly above a broad base to tip, sparsely to moderately glandular-pubescent adaxially. Corollas purple to blue (often with a white throat), yellow, or white, often with darker purple or blue veins, (13–)15–30(–35) mm, throat (1–)2–4(–5) mm diam., palatal folds slender to relatively broad, elongate or short; limb (1–)2–5(–8) mm.
Phenology: Flowering Apr–Aug.
Habitat: Sagebrush, hardwood and coniferous woodlands and forests, moist rock ledges, stream banks, meadows.
Elevation: 10–3200 m.
Distribution
Alta., B.C., Man., Sask., Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.
Discussion
Subspecies occidentalis has been divided into four infraspecific taxa in older literature. Two main groups of plants are the predominant hosts: Crassulaceae (Sedum) and Saxifragaceae (Lithophragma, Saxifraga, Tellima). However, several specimens have recorded or suggested parasitism on a variety of plants, even including mosses (Polytrichum), lycophytes (Selaginella), and ferns (Cryptogramma). Among the miscellaneous angiosperm reports are: Apiaceae (Lomatium, Perideridia), Asteraceae (Antennaria, Artemisia, Balsamorhiza, Coreopsis, Erigeron, Eriophyllum, Packera, Pseudognaphalium, Solidago), Caryophyllaceae (Eremogone), Liliaceae in the sense of this flora (Maianthemum), Poaceae (Bromus, Poa), Polemoniaceae (Leptodactylon), Ranunculaceae (Ranunculus), and Rubiaceae (Galium).
Based on two unusual specimens from Mohave County, Arizona, in which the proximal flowers were partially buried in loose substrate, B. D. Parfitt and M. L. Butterwick (1981) suggested that subsp. occidentalis might be capable of producing cleistogamous flowers. This condition has not been documented elsewhere among the holoparasitic taxa of Orobanchaceae in the region, except in Epifagus.
Selected References
None.