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Western Wetland Flora

Field Office Guide to Plant Species

Yellow Evening-primrose
Oenothera flava (A. Nels.) Garrett

JPG -- Species Photo JPG -- Distribution Map

Family: Evening-primrose (Onagraceae)
Flowering: May-July
Field Marks: The flowering stem of this plant has no leaves. The woody capsule is winged in the upper half.
Habitat: Low, dry depressions.
Habit: Perennial herb with a thick taproot.
Stems: Only the flower-bearing stem present, upright, up to 1 foot tall, smooth or hairy, the hairs sometimes glandular.
Leaves: All basal, narrowly oblong to oblanceolate, irregularly toothed or lobed, up to 8 inches long, up to 2 inches wide, smooth or glandular-hairy; leaf stalk slightly winged.
Flowers: Solitary at the tip of a leafless stem, opening in the evening, up to nearly 2 inches across.
Sepals: 4, green becoming purplish, more or less free from each other at the tip and pointing downward, becoming tubular below, the tube up to nearly 3 inches long.
Petals: 4, pale yellow, free from each other, 1/2-1 inch long.
Stamens: 6.
Pistils: Ovary inferior; stigmas 4.
Fruits: Capsules more or less woody, winged in the upper half, ovoid, 1/2-1 1/2 inches long, with minutely granular, obovoid seeds with a wing-like margin.

Previous Species -- Hooker's Evening-primrose (Oenothera elata )
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U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/plants/florawe/species/8/oenoflav.htm
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Page Last Modified: Saturday, 02-Feb-2013 06:28:10 EST
Reston, VA [vaww55]