Fibrous-rooted perennial to 1 m, simple or branched above, variously strigose or (especially upwards) spreading-hairy (but the hairs mostly shorter than in no. 15 [Oenothera pilosella Raf.]), or nearly glabrous below the infl, eglandular, or with only a few of the hairs gland-tipped; lvs narrowly elliptic to ovate or nearly linear, usually entire or nearly so, seldom over 6 cm; fls diurnal, out-crossing, several in a compact infl that only seldom nods at the tip; hypanthium 0.5-1.5 cm; sep (0.5-)1-2 cm, the tips short, usually free for only ca 1 mm or less; pet (1-)1.5-2.5 cm, notched at the summit; filaments 5-15 mm, alternately unequal; anthers 4-7 mm; style 12-18 mm; stigmas held above the anthers at anthesis; fr strongly tetragonal or narrowly 4-winged, evidently clavate or even obpyramidal, the body mostly 4-10 mm, tapering to a short or usually ±elongate pedicel-like base; 2n=28, 42, 56. Meadows, fields, and open woods, often in disturbed habitats; Mass. to Fla., w. to Ind., Mo., Okla., and La. June-Aug. (O. linearis; O. longipedicellata; Kneiffia allenii; K. f.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
