Martin and Hutchins 1980, Welsh et al. 1993, Kearney and Peebles 1969, Heil et al. 2013, Correll and Johnston 1970, Allred and Ivey 2012

Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Perennial herb, 10-50 cm tall, from a taproot and rhizome-like lateral roots; stems solitary or several from the base, the central stem erect and the others ascending; stems simple or branching throughout; stem epidermis white, exfoliating; herbage glabrous or covered with soft canescent or stiff hairs. Leaves: Alternate along the stems, and also in a basal cluster which occasionally persists until flowering; blades narrowly lanceolate to ovate, 2-4 cm long, the margins deeply runcinate-pinnatifid to sinuate-dentate or entire to serrate. Flowers: White and showy; sessile in the axils of upper leaves; hypanthium (floral tube at the base of the flower) slender and cylindric, 15-35 mm long; sepals 4 per flower, 12-18 mm long, pointed downward (reflexed) in full flower; petals 4, broadly obovate, 10-20 mm long, white when fresh and aging pink; flowers open near sunset. Fruits: Capsule cylindric, straight to curved or contorted, and tapering toward the apex, 15-60 mm long and 15-25 mm wide; splitting open longitudinally along 4 suture lines to release many seeds, these about 2 mm long. Ecology: Found on sandy soils to dry flats and slopes, from 3,500-8,000 ft (1067-2438 m); flowers May-September. Notes: Oenothera albicaulis appears similar with its white stems and similar growth form, but that species lacks the exfoliating epidermis on the stems that Oe. pallida has; also, Oe. albicaulis is an annual and lacks the rhizome-like lateral roots that this species has. There are three subspecies are worth noting in our region. Subsp. pallida is nearly hairless; has leaves with fine teeth along the edges; and a usually contorted seed pod. Subsp. runcinata is sparsely to densely strigillose (with short, sharp appressed hairs) on the upper stems and leaves, or else mostly glabrous; is much-branched above the base and stoutly perennial, even becoming a subshrub; and usually has a straight or curved seed pod. Subsp. trichocalyx is conspicuously villous (covered with long soft hairs) on the upper stems and leaves; usually has a contorted capsule; and has few branches above the base, being a shorter-lived perennial or even annual. Ethnobotany: Used as a ceremonial emetic, for venereal disease, sores, spider bites, kidney disease, snake bites, sore throat, and in other ceremonial ways. Etymology: Oenothera comes from the Greek oinos, wine, and therao, to seek or imbibe, alluding to the fact that the root of Oenothera biennis was used to flavor wine; pallida means pale, in reference to the often pale leaves. Synonyms: None Editor: SBuckley 2010, AHazelton 2017