待宵草 dai xiao cao

Herbs erect or rarely decumbent, annual or biennial, often with basal rosette. Stems 25-100 cm tall, simple or barely branched, strigillose, often with spreading and glandular hairs. Leaves green, with inconspicuous veins, strigillose, sessile to shortly petiolate; rosette leaves 10-25 × 0.8-2.5 cm; cauline leaves very narrowly elliptic to lanceolate or oblanceolate, 6-18 × 0.6-2.5 cm, base attenuate, rounded, or cordate, margin serrate and usually somewhat undulate, apex acute. Inflorescence a lax open simple or branched spike. Flowers open near sunset, one or several per day; floral tube 2-3.5 cm, erect in bud. Sepals 1.2-2.5 cm, with free tips 1-3 mm, erect. Petals yellow, often with a red spot at base, fading to reddish orange, 1.5-2.5(-3.5) cm. Anthers 7-11 mm; pollen ca. 50% fertile. Ovary densely strigillose, with some longer spreading or glandular hairs; stigma surrounded by anthers. Capsules cylindric, somewhat enlarged toward apex, 2-4 cm, sessile. Seeds in two rows per locule, brown, ellipsoid, 1.4-1.8 mm, inconspicuously pitted. Fl. May-Nov, fr. Jun-Nov. 2n = 14, permanent translocation heterozygote; self-compatible, mostly autogamous.

Moist, disturbed habitats near streams, roadside ditches, usually escaped from cultivation; 600-2500 m. Fujian, Guangxi, Guizhou, Hubei, Jiangxi, Shaanxi, Shandong, Sichuan, Taiwan, Yunnan [India, Indonesia, Japan, Pakistan, Russia, Sri Lanka; native to South America (Chile and Argentina); naturalized in Africa, SW Asia, Australia, Europe, North America, and Pacific islands].

This species, sometimes cultivated for its relatively large, attractive flowers, often becomes naturalized in China and elsewhere. Many specimens from China have been determined as Oenothera odorata Jacquin; however, that species, also native to S South America but rarely, if ever, naturalized elsewhere, differs from O. stricta by having narrower leaves, larger petals that lack a red spot at the base, shorter floral tubes, and bracts mostly longer than the capsules they subtend.