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Camissonia pterosperma (S. Wats.) Raven

Wing-seeded evening-primrose

Onagraceae (Evening-primrose family)

General Description: A slender, simple or branched, diminutive annual herb up to about 15 cm tall. The herbage has few to many tiny spreading hairs and becomes glandular in the inflorescence. Stem leaves are entire, mostly lance-shaped, and up to about 1.5 cm long (occasionally longer) and 5 mm wide. Flowers are erect on short pedicels in the upper leaf axils. The petals are small, 1.5-3 mm long, white with a yellow base, aging to a pinkish color. Sepals are small and reflexed. The fruit capsule is more or less straight, cylindric, shortly stalked, 1-2 cm long, and slightly to more often widely spreading by maturity. Seeds have a pair of conspicuous, incurved marginal wings.

Illustration.

Field Identification Tips: The slender, diminutive habit, entire, narrow leaves, small white flowers with a yellow base, and shortly-stalked, straight fruit capsules are good field characteristics. The white flowers with a yellow base and seeds having a pair of conspicuous, thick, incurved marginal wings are diagnostic.

Phenology: Flowers from approximately mid-May to mid-June.

Similar Species: There are several other annual Camissonia species in east-central Idaho. They all differ in one or more readily viewed field characteristics, including, having toothed versus entire leaves; having mostly basal leaves versus leaves mostly along the stem; having sessile versus stalked fruit capsules; having bent/contorted versus straight fruit capsules; or having yellow versus white flowers. The elongated fruit capsule positioned below (inferior) the sepals distinguishes species of Camissonia from most other small annual forb species encountered in east-central Idaho.

Habitat: Dry, open slopes, ridges, and washes in the sagebrush and juniper zones. Most known Idaho populations occur on gravelly-silty soils, on southerly-facing limestone slopes. It is also known from volcanic-derived substrates in a few places. The vegetation is dominated by open Juniperus osteosperma, Artemisia arbuscula, or Artemisia nova communities. Other associated species in this open habitat include Pseudoroegneria spicata, Poa secunda, Achnatherum hymenoides, Eriogonum spp., Phlox hoodii, and Mentzelia albicaulis.

Global Distribution: Southeastern Oregon and adjacent very southwestern Idaho, south through Nevada to Inyo County, California, northern Arizona, and portions of Utah; then disjunct in east-central Idaho.

Idaho Distribution: Most Idaho populations of wing-seeded evening-primrose are known from the low, southern ends of the Lost River, Lemhi, and Beaverhead ranges in Butte and Clark counties. It has also been collected from near the South Fork Owyhee River in Owyhee County, in very southwestern Idaho.

References:

Cholewa, A. F., and D. M. Henderson. 1984. A survey and assessment of the rare vascular plants of the Idaho National Engineering Laboratory. DOE/ID-12100. U.S. Department of Energy, Idaho Operations Office, Radiological and Environmental Sciences Laboratory, Idaho Falls, ID. 45 pp.

Cronquist, A., N. H. Holmgren, and P. Holmgren. 1997. Intermountain Flora. Vascular plants of the Intermountain West, U.S.A. Vol. 3, Part A. The New York Botanical Garden, Bronx, NY. 446 pp.