30. Oenothera fruticosa Linnaeus, Sp. Pl. 1: 346. 1753.
[E]
Kneiffia fruticosa (Linnaeus) Spach ex Raimann
Herbs perennial, moderately to densely strigillose and/or villous, glandular puberulent, or glabrous; from fibrous roots, not or rarely producing rhizomes. Stems erect to decumbent, branched or unbranched, (10–)30–80 cm. Leaves in a basal rosette and cauline, rosette usually withered by anthesis, surfaces sometimes glaucous, especially abaxially, basal 3–12 × 0.5–3 cm, petiole 1–4 cm, blade oblanceolate to obovate, margins subentire, dentate, or denticulate, sometimes undulate; cauline 2–6(–11) × (0.1–)0.5–2(–5) cm, petiole 0.1–2(–6) cm, blade linear, lanceolate to oblanceolate, narrowly elliptic, or ovate, margins subentire or dentate or denticulate, sometimes undulate. Inflorescences usually erect, rarely nodding, flowers in axils of distalmost few nodes. Flowers opening near sunrise; buds with free tips 0.5–8(–13) mm, connivent, sometimes spreading; floral tube 5–20 mm; sepals 5–20 mm; petals pale to bright yellow, fading pale pink, orangish pink, or yellow, (8–)15–25(–30) mm; filaments 5–15 mm, anthers 4–7 mm, pollen 85–100% fertile; style 12–20 mm, stigma exserted beyond anthers at anthesis. Capsules clavate to oblong-clavate or oblong-ellipsoid, 4-angled to 4-winged, (5–)10–17(–20) × (2–)3–4(–6) mm, stipe 0.1–10 mm; sessile. Seeds 1 × 0.5 mm.
Subspecies 2 (2 in the flora): c, e North America.
Oenothera fruticosa as delimited here is a polymorphic species. Previous classification of this group has undergone numerous reorganizations due to the difficulties in separating populations into discrete morphological taxa. In the past it has most frequently been treated as two species, O. fruticosa and O. tetragona Roth, often with a dozen or more infraspecific taxa recognized. The broad delimitation of G. B. Straley (1977) is followed here with one species consisting of two subspecies that appear to intergrade extensively across a wide area of overlap. Straley determined O. fruticosa to be self-incompatible and polyploid.
