Obscure Evening-primrose - Camissonia andina
Oenothera andina, Holmgrenia andina
State Rank Reason (see State Rank above)
This species is at the edge of its range in Montana, where it has been documented from just a few locations. All known extant locations are from Carbon County. These populations collectively cover less than 20 acres, but they can vary greatly in size from year to year. It tolerates grazing well, and moderate grazing may be important in maintaining a suitable seedbed of exposed soil. Invasive weeds may pose the greatest risk.
Obscure Evening-primrose is a small annual herb with stems, 3-15 cm high, that branch from the base and make the plant broader than it is tall. The strap-shaped leaves, 5-25 mm long, are clustered at the base of the plant and at the upper portions of the stems. Foliage is finely hairy. Tiny flowers are attached to the stem at the base of upper leaves. The 4 separate, yellow petals are 1-2 mm long, and the 4 sepals are reflexed. The stigma is ball-shaped. Petals and sepals are attached at the top of the ovary, which matures into a narrowly club-shaped capsule, 4-8 mm long, with the widest point attached to the stem.
Wagner et al. (2007, Syst. Bot. Monogr. Vol. 83; but see also Wagner & Hoch 2009 [Novon 19:130-132]) treat this as Neoholmgrenia andina (Nutt.) Wagner & Hoch.
Flowering occurs in May and June.
Several other species of small evening-primroses occur in Montana. Oenothera scapoidea (=Cyclismia s.) has stalked fruits, O. minor (=Eremothera m.) has white flowers, and O. parvula has larger petals and a more open inflorescence.
BC, MT south to CA, NV, UT and WY (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Obscure evening-primrose is found in exposed sandy soil of dry prairie slopes, flats and depressions, in moist swales on south-facing hillsides, and in sagebrush (Kershaw et al. 2001). On the south side of the Pryor Mountains, where the majority of -- and all recently documented -- Montana populations are located, it occurs from 1220 to 1890 m (4000-6200 feet) in the foothills, with the shrubs Artemisia tridentata and Cercocarpus ledifolius, and occasionally in Douglas fir-Utah juniper woodland (Lesica and Achuff 1992).
Since this species is a small annual, it may benefit from moderate levels of disturbance (Lesica and Achuff 1992). Population sizes can vary greatly from year to year. Seeds may remain dormant during years with unfavorable growing conditions.
This small evening-primrose can tolerate heavy grazing, and some disturbance from moderate grazing may be needed to provide a suitable seedbed of exposed soil (Kershaw et al. 2001). Invasive weeds pose a threat to at least one population.
- Additional ReferencesLegend: View Online Publication
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- Kershaw, L., J. Gould, D. Johnson & J. Lancaster. 2001. Rare vascular plants of Alberta. University of Alberta Press, Edmonton, Alberta, Canada. 484 pages.
- Lesica, P. and P.L. Achuff. 1992. Distribution of vascular plant species of special concern and limited distribution in the Pryor Mountain desert, Carbon County, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 105 pp.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.