Perennial by creeping roots (sometimes annual?), ascending to erect, 1-6 dm; lvs linear to lanceolate or oblanceolate, 3-8 cm, gradually tapering to a petiolar base, entire to runcinate-pinnatifid, the basal half commonly more coarsely toothed than the upper; fls few, sessile in the upper axils, erect, buds nodding, long-acuminate; hypanthium slender, 1-2 cm, strigose; sep lance-linear, reflexed at anthesis, 1.5-2.5 cm, usually long connivent; pet obcordate, white or pink, 2-4 cm; stamens alternately unequal; fr narrowly obovoid or clavate, 10-18 mm, 4-sided, roundly 8-ribbed and deeply sulcate, tapering to both ends, sterile below; 2n=14. Dry, open places; Mo. and Kans. to Tex., and intr. eastward. May, June. (Hartmannia s.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Kearney and Peebles 1969, McDougall 1973, Wagner et. all 2007
Duration: Perennial Nativity: Native Lifeform: Subshrub General: Herbaceous to suffrutescent perennials, stems several, slender, branching or occasionally simple, herbage pubescent, plants with creeping rhizomes. Leaves: Alternate, cauline or in a basal rosette, blades elliptic to elliptic-oblanceolate or ovate, sometimes lanceolate, cauline leaves 1-7 cm long, margins subserrate to weakly sinuate-dentate or occasionally sinuate-pinnatifid, short-petioled to subsessile. Flowers: White to rose-colored, petals obcordate, 2.5-4 cm long, sepals 1-2 cm long, the long-acuminate lobes united but free at the tips, calyx, stamens, borne few to several in upper leaf axils, nodding in bud on reflexed stems, buds rounded in cross-section with free tips to 4 mm long, flowers opening in the evening. Fruits: Capsules club-shaped, strongly 8-ribbed, the main body 3-5 mm thick and attenuate to a slender base, the upper face of each valve with a prominent rib. Seeds obovoid to fusiform, clustered in 2 or more rows in each cell. Ecology: Found from 3,000-3,500 ft (914-1067 m); flowering May-June. Distribution: Missouri and Kansas to Texas, Arizona, and Mexico. Notes: Look to the nodding buds and the white to pink flower petals 2.5-4 cm long to help identify this species. Ethnobotany: There is no use recorded for this species, but other species in this genus have uses. Etymology: Oenothera is from Greek oinos, wine and thera, to imbibe, while speciosa means showy. Synonyms: None Editor: LCrumbacher 2012
From Flora of Indiana (1940) by Charles C. Deam
I have collected this species from the side of a railroad, a roadside to which it had escaped from a cemetery, and a roadside where it was common, and also in an adjoining alfalfa field. I planted some of it and when, in two years, it had spread by underground rootstocks over a large area, it became necessary to destroy it and the process required three years of careful work. Since I never permitted it to seed I do not know its ability to propagate from seed but most species of this genus should be regarded with suspicion. This species, no doubt, in time will become an obnoxious weed.
Indiana Coefficient of Conservatism: C = null, non-native