Rose Evening Primrose

One collection of Oenothera rhombipetala Nutt. ex Torr. & A. Gray has been collected in Afghanistan, Mazar-i-Sharif, Koelz 13192 (NA), and perhaps it may also occur in Pakistan. This species is easily distinguished from the others by its dense terminal spikes 1-3 dm long of yellow flowers, the slender buds 2-4 mm in diameter, rhombic-obovate petals and arcuate-cylindric capsules 12-16 mm long and ca. 2.5 mm in diameter. Oenothera rhombipetala is native in the Great Plains of the United States.

Herbs ascending to decumbent, perennial, rhizomatous and sometimes suffrutescent from woody caudex, rarely with basal rosette. Stems 7-65 cm, simple or branched, strigillose, sometimes with longer spreading hairs. Leaves green, with inconspicuous veins, glabrous to sparsely strigillose; petioles 3-20 mm; basal blade 2-5 × 0.5-2 cm; cauline blade elliptic to oblanceolate or oblong-ovate, 1-6 × 0.4-2.5 cm, base attenuate, margin subentire to coarsely dentate, sometimes sinuate-pinnatifid at leaf base, apex acute to obtuse. Inflorescence a lax open simple raceme. Flowers open near sunrise; floral tube 4-10 mm. Sepals 5-10 mm, with free tips 0.4-1 mm. Petals pink to rose-purple, 5-12 mm. Anthers 2-3.5 mm; pollen ca. 50% fertile. Ovary usually densely strigillose; stigma surrounded by anthers. Capsules clavate or narrowly obovoid, 4-12 mm, valves angled or weakly winged, attenuate to slender sterile stipe (pedicel) 5-20 mm. Seeds in several indistinct rows per locule, brown with dark spot at each end, obovoid, 0.5-1.2 mm, finely papillose. Fl. May-Nov, fr. Jun-Dec. 2n = 14, permanent translocation heterozygote; self-compatible, autogamous.

Well-branched perennial herb, flowering the first year, stems ascending, 1-4 dm tall, densely strigillose, rarely mixed with sparse villous hairs. Leaves subentire or sinuate-pinnatifid, elliptic or rarely narrowly ovate, 2-5 x 1-2.5 cm, the petiole 2-25 mm long. Flowers opening near sunrise; mature buds erect. Floral tube 4-8 mm long. Sepals 7-12 mm long; sepal tips 0.1-0.5 mm long. Petals rose to rose-purple, obovate, 4-12 mm long. Style 0.8-1.4 cm long; the stigma surrounded by the anthers at anthesis. Capsule clavate, 1.3-3 cm long, tapering to a sterile stipe-like portion 0.5-2 cm long, the ridge on each valve ± prominent, the valve narrowly winged. Seeds in several indistinct rows in each locule, oblong-obovoid to obovoid, 0.7-0.9 mm long, the surface finely granular, with a dark spot at each end. Self-compatible and self-pollinating. Gametic chromosome number, n = 7 (rings of 14 in meiotic metaphase I).

Native of Peru; widely naturalised in Europe, Himalaya, India, Burma.

Guizhou, Jiangxi, Sichuan, Yunnan, Zhejiang [Japan; native to S North America and N South America, frequently cultivated and naturalized in SW Asia, Australia, Europe, and South America].

Distribution: Native from central and southern Texas, USA, throughout Mexico and Central America to El Salvador, and throughout South America; naturalized throughout the warmer regions of the world. Sandy to clay soils, along creeks or in low weedy places, l000-2000 m elev. According to Stewart (loc. cit. 508. 1972), O. rosea is an old introduction from Mexico, which has run wild in many areas of Pakistan. He lists the following additional localities for which I have not seen specimens: Hazara, Poonch, Kashmir, Jhelum Valley. Fl. Per.: Apr-Sep.

1100-2500 m

Disturbed habitats along creeks and in low weedy places; 1000-2000 m.

Hartmannia rosea (L' HJr. ex Ait.) G. Don in Sweet, Hort. Brit. ed. 3. 236. 1839.