Raimannia Rose ex Britton & A. Brown, Ill. Fl. N. U.S. ed. 2, 2: 596, figs. 3042–3044. 1913; Oenothera sect. Raimannia (Rose ex Britton & A. Brown) Munz; Oenothera ser. Raimannia (Rose ex Britton & A. Brown) W. Dietrich & W. L. Wagner; Oenothera subg. Raimannia (Rose ex Britton & A. Brown) Munz

Herbs annual or short-lived perennial; from taproot. Stems erect, ascending, or decumbent. Flowers: buds erect, terete to weakly quadrangular, with free tips terminal, erect or spreading; floral tube curved upward, 12–50 mm; petals broadly obcordate, sometimes shallowly so. Capsules usually straight, sometimes curved upward, cylindrical, sometimes slightly enlarged toward apex, subterete, 2–4(–5) mm diam. Seeds in 2 rows per locule, brown, ellipsoid to subglobose, surface reticulate and regularly pitted. 2n = 14.

Species 6 (6 in the flora): c, s United States, n Mexico, West Indies (Cuba), Bermuda; intro­duced nearly worldwide in temperate and subtropical areas.

Subsection Raimannia consists of six diploid (2n = 14) species native to North America, primarily in the south-central United States, with some species extending into Mexico in Tamaulipas (Oenothera grandis), Campeche, and Baja California (O. drummondii) (W. Dietrich and W. L. Wagner 1988). Several species are widespread, including O. laciniata in most of eastern North America and naturalized in Australia, Europe, Hawaiian Islands, Japan, Paraguay, and South Africa; O. drummondii also is widely naturalized, in Australia, Europe, North Africa and the Middle East, China, South America, and South Africa. P. A. Munz (1965) included these species in his rather heterogeneous and broadly delimited subg. Raimannia, which consisted of species here assigned by Wagner et al. (2007) to sects. Kleinia and Ravenia W. L. Wagner, and Oenothera subsects. Candela, Emersonia, Munzia, and Nutantigemma, in addition to those retained here in subsect. Raimannia. Dietrich (1977) removed the South American species to a new subsect. Munzia. The current, narrower circumscription is based primarily on a wide series of crossing experiments (W. Stubbe and P. H. Raven 1979; Dietrich and Wagner). Oenothera drummondii, O. falfurriae, O. grandis, and O. mexicana are bivalent-forming species (2n = 14), whereas O. humifusa and O. laciniata are PTH. Oenothera grandis is self-incompatible, while the other species are self-compatible and largely autogamous, except O. drummondii, which, like O. grandis, is outcrossed by hawkmoths (Dietrich and Wagner).