Oenothera Linnaeus (sect. Lavauxia) subsect. Lavauxia in Flora of North America @ efloras.org

1717c.1. Oenothera Linnaeus (sect. Lavauxia) subsect. Lavauxia (Spach) W. L. Wagner & Hoch, Syst. Bot. Monogr. 83: 150. 2007.

Lavauxia Spach, Hist. Nat. Vég. 4: 366. 1835

Flowers petals yellow, fading orange, drying purple to lavender. Capsules narrowly winged, wings oblong or triangular (O. triloba) in distal 2/3. 2n = 14.

Species 3 (3 in the flora): w North America, n, c Mexico.

Subsection Lavauxia consists of three yellow-flowered species that are native from southern Alberta and southwestern Saskatchewan, scattered in the western United States and east through Kansas, Missouri south of the Missouri River, northern Arkansas, Texas, northern Alabama, and Kentucky, south into Mexico from the Sierra Madre Occidental to the Trans-Mexican Volcanic Belt in Guanajuato and Hidalgo, and disjunct in the mountains of Baja California, at 300–3200 m elevation. One species (O. triloba) is introduced in the eastern United States.

1 Petals pale yellow; capsules woody, with broad, triangular wings 5–10 mm wide, these often terminating in a hooked tooth; herbs annual or, sometimes, biennial 14 Oenothera triloba

+ Petals bright yellow; capsules leathery, with narrowly oblong wings 1–5(–6) mm wide, not with a hooked tooth; herbs perennial, rarely short-lived. (2)

2 (1) Leaves moderately stiff, blades linear to narrowly elliptic, margins irregularly and coarsely dentate; petals fading deep reddish orange, drying purplish brown; lateral roots often producing adventitious shoots; capsules 14–18(–22) mm, valve wings 1–2(–4) mm wide 12 Oenothera acutissima

+ Leaves flexible, sometimes ± fleshy, blades oblanceolate to linear-oblong, margins usually irregularly and coarsely pinnately lobed, rarely subentire; petals fading pale orange, drying purple; lateral roots not producing adventitious shoots; capsules (10–)20–35(–43) mm, wings (2–)3–5(–6) mm wide 13 Oenothera flava