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Oenothera engelmannii   (Small ) Munz
Morton County, Kansas (photo by Marion McGlohon)
Height: 8-30 inches
Family: Onagraceae - Evening-primrose Family
Flowering Period:   May, June, July, August, September
Stems: Spreading to ascending or erect, branched below, villous; epidermis white or greenish white, exfoliating.
Leaves: Basal and cauline, alternate; basal sometimes withering before flowering, blades 1 to 4.8 inches long, 1/6 to 1 inch wide, margins sinuate-dentate to pinnately lobed; cauline sometimes withering proximally, sessile or short-petiolate, blades oblong-lanceolate to lanceolate, 2/5 to 3.2 inches long, 1/12 to 4/5 inch wide, margins sinuate-dentate to coarsely dentate or pinnately lobed, surfaces glabrate or finely strigose.
Inflorescences: Axillary, flowers solitary.
Flowers: Radially symmetric; hypanthium 4/5 to 1.2 inch, pilose and finely strigose; sepals 4, deciduous, absent on fruit, reflexed, lanceolate, 2/5 to 4/5 inch, distinct at flowering; petals white, fading pink, 4, broadly obovate, 1/2 to 4/5 inch, tip rounded or slightly emarginate; stamens 8, anthers 1/6 to 1/4 inch; stigma positioned above anthers, deeply 4-lobed, lobes 1/12 to 1/7 inch.
Fruits: Capsules, stiffly spreading, lanceoloid, 1 to 2 inches long, 1/25 to 1/7 inch wide, straight or slightly curved, 4-angled, finely strigose and with spreading hairs; seeds many per fruit, reddish brown, linear-obovoid, 1/25 to 1/15 inch, smooth or obscurely longitudinally striate.
Habitat: Sandsage prairies
Distribution: Southwest corner of Kansas
Origin: Native
Comments: Named for American botanist George Engelmann.

Engelmann's evening-primrose
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Morton County, Kansas (photo by Marion McGlohon)