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Oenothera biennis

Description from Flora of China

Oenothera muricata Linnaeus; O. suaveolens Desfontaines; Onagra biennis (Linnaeus) Scopoli; O. muricata (Linnaeus) Moench.

Herbs erect, biennial, with basal rosette. Stems 30-200 cm tall, simple or sparsely branched, densely to very sparsely strigillose and with longer spreading and usually pustulate-based hairs, inflorescence often also glandular puberulous. Leaves green or pale green, with inconspicuous veins, sessile or shortly petiolate; rosette blade 10-30 × 2-5 cm; cauline blade narrowly oblanceolate to elliptic, 5-22 × (1-)1.5-5(-6) cm, base acute to attenuate, margin dentate to subentire, often lobed near base, apex acute. Inflorescence a dense mostly unbranched spike. Flowers open near sunset; floral tube (2-)2.5-4 cm. Sepals 1.2-2.2(-2.8) cm, with free tips 1.5-3 mm, erect. Petals yellow, fading to orange, 1.2-2.5(-3) cm. Anthers 3-6(-9) mm; pollen ca. 50% fertile. Ovary densely glandular puberulous and sparsely villous or with very sparse pustulate-based hairs, sometimes only densely strigillose; stigma surrounded by anthers. Capsules green, narrowly lanceoloid to lanceoloid, 2-4 cm, sessile. Seeds in two rows per locule, brown to nearly black, 1.1-2 mm, irregularly pitted. Fl. Jul-Oct, fr. Jul-Nov. 2n = 14, permanent translocation heterozygote; self-compatible, autogamous.

The seeds of this species contain gamma linolenic acid (GLA), an anti-inflammatory compound of potential therapeutic use for cardiovascular disorders, arthritis, and other human diseases. The cultivation of these plants as a source of GLA has increased recently, and the species has become naturalized widely in China.

Common in open, disturbed areas; near sea level to 1500 m. Anhui, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jilin, Liaoning, Nei Mongol, Sichuan, Taiwan, Yunnan [Bhutan, Japan, Kazakhstan, Korea, Kyrgyzstan, Russia; native to E North America; widely naturalized in SW Asia, Europe, Pacific islands (New Zealand), and S South America].


 

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