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.

Distribution

c, s United States, n Mexico, West Indies (Cuba), Bermuda, intro­duced nearly worldwide in temperate and subtropical areas.

Discussion

Species 6 (6 in the flora).

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).

Selected References

None.

Lower Taxa

Oenothera drummondii, Oenothera falfurriae, Oenothera grandis, Oenothera humifusa, Oenothera laciniata, Oenothera mexicana

Key

1	Plants densely strigillose, sometimes also villous, becoming glandular puberulent distally; leaf blades grayish green, margins subentire or remotely, shallowly dentate; bracts flat; coastal sites.	> 2
2	Sepals 20–30 mm; petals 20–45 mm; stigmas exserted beyond anthers at anthesis; pollen 85–100% fertile.	Oenothera drummondii
2	Sepals 3–11 mm; petals 4.5–16 mm; stigmas surrounded by anthers at anthesis; pollen ca. 50% fertile.	Oenothera humifusa
1	Plants moderately to sparsely strigillose, usually also sparsely to sometimes densely villous, usually also glandular puberulent distally; leaf blades green, margins usually deeply lobed to dentate or pinnatifid, rarely subentire; bracts flat or, if grayish green, then margins revolute; inland sites, often in disturbed habitats.	> 3
3	Petals 25–40 mm; styles 40–75 mm, stigmas exserted beyond anthers at anthesis; pollen 85–100% fertile.	Oenothera grandis
3	Petals 5–25 mm; styles 20–50 mm, stigmas surrounded by, or slightly exserted beyond, anthers at anthesis; pollen 50–100% fertile.	> 4
4	Bracts revolute, distalmost erect.	Oenothera mexicana
4	Bracts flat, distalmost spreading.	> 5
5	Petals 13–25 mm; stigmas slightly exserted beyond anthers at anthesis; pollen 85–100% fertile.	Oenothera falfurriae
5	Petals 5–22 mm; stigmas surrounded by anthers at anthesis; pollen ca. 50% fertile.	Oenothera laciniata