Oenothera acutissima
Author: W.L. Wagner

Narrow-leaf evening primrose

Onagraceae (Evening Primrose Family)

Close up of Oenothera acutissima by Renee Rondeau
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Close up of Oenothera acutissima by Renee Rondeau
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Close up of Oenothera acutissima by Jennifer Ramp Neale
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Ranks and Status

Global rank: G2
State rank: S2
Federal protection status: BLM Sensitive
State protection status: None

[+] Description and Phenology

Artwork by Julie Ann Terry. Please also see 1997 profile.
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General description: Perennial forb with a basal rosette and a long branching, woody taproot. The linear leaves are bright green to grey-green, moderately thick and stiff, and irregularly dentate. The petals are reddish-orange before blooming, turning yellow with flowering (Denver Botanic Gardens 2008). The hypanthium is prolonged beyond the ovary as a slender tube.  Dehiscent capsule is 4-winged; capsule wings are 2-5 mm wide (Spackman et al. 1997).

Look Alikes: Oenothera flava taproot is fleshy and stout, and capsule wings are 1-2 mm wide (Spackman et al. 1997).

Phenology: Flowers in late May-June. Flowers open in the evening, and close by mid-morning (Spackman et al. 1997).

[+] Habitat

Habitat of Oenothera acutissima by Michelle Deprenger-Levin
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Habitat of Oenothera acutissima by Pam Regensberg
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Habitat of Oenothera acutissima by Jennifer Ramp Neale
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Restricted to sandy, gravelly and rocky soils, in seasonally wet areas; in meadows, depressions, or along arroyos in mixed conifer forest to sagebrush scrub (Wagner 1981). This species occurs in short outcrops or "rock reefs", drainages, and gullies (pers. comm. Densie Culver 2014).

Elevation Range: 5,298 - 9,108 feet (1,615 - 2,776 meters)

[+] Distribution

Distribution of Oenothera acutissima in Colorado.
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Colorado endemic: No
Global range: Restricted to Moffat County, Colorado and Daggett, Uintah, and Duchesne counties, Utah; Duchesne County, UT has just one occurrence. The Center for Native Ecosystems and Colorado Native Plant Society (2006) describe the range as "in the vicinity of the Flaming Gorge National Recreation Area and around Diamond Mountain, Cold Spring Mountain, and Douglas Mountain at the eastern end of the Uinta Mountains. It has been found as far west as Burnt Mill Spring, northwest of Roosevelt, and as far east as Boone Draw, below Sand Wash Basin in Moffat County, Colorado... The Uinta Mountains are relatively isolated from other mountain environments with similar elevational characteristics, and this isolation likely sets a natural limit on the geographic distribution." Range extent is approximately 5000 - 5500 square km when calculated using GIS tools.
State range: Known from Moffat County in Colorado. Estimated range in Colorado is 1523 square kilometers (588 square miles), calculated in GIS by drawing a minimum convex polygon around the known occurrences (calculated by the Colorado Natural Heritage Program in 2008). Also known from Utah.

[+] Threats and Management Issues

Summary results of an analysis of the status of Oenothera acutissima based on several ranking factors. This species was concluded to be “weakly conserved”. From Rondeau et al. 2011.
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The primary threat at this time is considered to be hydrologic alteration (Rondeau et al. 2011). It is not known if all of the occurrences are or are not threatened by these activities. Mesic areas and ephemeral creek bottoms in which this species occurs are often degraded by domestic livestock. Hydrologic alterations associated with livestock grazing (e.g. expansion of seasonal ponds/depressions) and associated trampling are potential threats to the species. As a species/habitat sensitive to decreased precipitation levels, Oenothera acutissima may be particularly vulnerable to climate change. This species occurs primarily on BLM and private land with no special protection status. Additionally, there is oil and gas development in the area, which could impact the plants.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Center for Native Ecosystems and Colorado Native Plant Society. 2006. Petition to List Narrowleaf Evening Primrose (Oenothera acutissima) as Threatened or Endangered and Designate Critical Habitat under the Endangered Species Act (16 U.S.C. § 1531, Et Seq.). Submitted 12 April 2006. Online. Available: www.nativeecosystems.org/species/narrowleaf-evening-primrose/index_html/ (Accessed 2008)
    • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 pp.
    • Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, P.K. Holmgren. 1997. Intermountain Flora, Volume 3, Part A Subclass Rosidae (except Fabales). The New York Botanical Gardens. Bronx, New York. 446 pp.
    • Dawson, C. 2009. Personal communication regarding BLM rare plant monitoring in Colorado.
    • Denver Botanic Gardens. 2008. Report to the Bureau of Land Management on the survey work conducted for Oenothera acutissima W.L. Wagner (Flaming Gorge or narrowleaf evening primrose) by Denver Botanic Gardens in 2008. Unpublished report. 8 pp.
    • Goodrich, S., and E. Neese. 1986. Uinta Basin flora. U.S. Forest Service, Intermountain Region, Ogden, Utah. 320 pp.
    • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
    • Neely, B., S. Panjabi, E. Lane, P. Lewis, C. Dawson, A. Kratz, B. Kurzel, T. Hogan, J. Handwerk, S. Krishnan, J. Neale, and N. Ripley. 2009. Colorado Rare Plant Conservation Strategy, Developed by the Colorado Rare Plant conservation Initiative. The Nature Conservancy, Boulder, Colorado, 117 pp.
    • Raguso, R. A., A. Kelber, M. Pfaff, R. A. Levin, and L. A. McDade. 2007. Floral biology of North American Oenothera sect. Lavauxia (Onagraceae): Advertisements, rewards, and extreme variation in floral depth. Annals of the Missouri Botanical Garden 94(1): 236-257.
    • Rondeau, R., K. Decker, J. Handwerk, J. Siemers, L. Grunau, and C. Pague. 2011. The state of Colorado's biodiversity 2011. Prepared for The Nature Conservancy. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado.
    • Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. (Web authors: Johnson, C.S. and M. Barry). 1999. Colorado rare plant field guide. Prepared for Bureau of Land Management, U.S. Forest Service and U.S. Fish and Wildlife Service by Colorado Natural Heritage Program. Online. Available: http://www.cnhp.colostate.edu/rareplants/cover.html (Accessed 2006)
    • The Colorado Native Plant Society. 1997. Rare Plants of Colorado, second edition. Falcon Press Publishing Co.,Inc. Helena, Montana. 105pp.
    • U.S. Fish and Wildlife Service (USFWS). 2009. Endangered and Threatened Wildlife and Plants; 90-Day Finding on a Petition To List Oenothera acutissima (Narrowleaf Evening-primrose) as Threatened or Endangered. Federal Register, 74(109): 27266-27271.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Utah Native Plant Society. 2003-2007. July 30 last update. Utah Rare Plant Guide. Salt Lake City, UT. Online. Available: http://www.utahrareplants.org (accessed 2007).
    • Wagner, W. L. and P. C. Hoch. 2005-. Onagraceae, The Evening Primrose Family website. Online. Available: http://botany.si.edu/onagraceae/index.cfm (Accessed 2008).
    • Wagner, W.L. 1981. Oenothera acutissima (Onagraceae), a new species from northwestern Colorado and adjacent Utah. Systematic Botany 6(2): 153-158.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Western Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 532 pp.
    • Welsh, S.L., N.D. Atwood, S. Goodrich, and L.C. Higgins (eds.) 1993. A Utah flora. 2nd edition. Brigham Young Univ., Provo, Utah. 986 pp.

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