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Oenothera berlandieri   (Spach ) Steud.
[=Calylophus berlandieri Spach]
[=Calylophus drummondianus Spach  subsp. berlanderi  (Spach ) Towner & Raven]
Oklahoma panhandle (photo by Marion McGlohon)
Height: 4-30 inches
Family: Onagraceae - Evening-primrose Family
Flowering Period:   April, May, June, July, August
Stems: Decumbent to erect, simple or branched, glabrous or finely strigose to canescent; epidermis green or brown, sometimes exfoliating.
Leaves: Cauline, alternate, sessile; blade spatulate to narrowly lanceolate or linear, 1/2 to 3.5 inches long, 1/25 to 2/5 inch wide, margins nearly entire to serrate, surfaces glabrous or finely strigose to canescent.
Inflorescences: Axillary, flowers solitary.
Flowers: Radially symmetric; hypanthium 1/5 to 4/5 inch, glabrous or finely strigose to canescent; sepals 4, deciduous, absent on fruit, reflexed, triangular, 1/5 to 1/2 inch, with conspicuously keeled midrib; petals yellow, 4, nearly orbiculate, obovate, or obcordate, 2/5 to 1 inch, tip rounded to truncate or shallowly notched; stamens 8, of 2 lengths; anthers 1/7 to 1/5 inch; stigma positioned above anthers, somewhat 4-angled.
Fruits: Capsules, ascending, cylindric, 2/5 to 1.6 inch long, 1/25 to 1/12 inch wide, straight or slightly curved, 4-angled, strigose; seeds many per fruit, brown, obliquely truncate and angled, 1/25 to 1/12 inch, obscurely roughened.
Habitat: Rocky to sandy shortgrass prairies
Distribution: Southwest corner of Kansas
Origin: Native
Comments: Named for French botanist Jean Louis Berlandier. Oenothera has been expanded to include Calylophus, a genus formerly recognized as separate in the Great Plains.

Berlandier's evening primrose
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Oklahoma panhandle (photo by Marion McGlohon)
Berlandier's evening primrose
157 KB
Oklahoma panhandle (photo by Marion McGlohon)