Astragalus debequaeus
Author: Welsh

DeBeque milkvetch

Fabaceae (Pea Family)

Close up of Astragalus debequaeus by Peggy Lyon
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Close up of Astragalus debequaeus by Georgia Doyle
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Close up of Astragalus debequaeus flowers by Georgia Doyle
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Close up of Astragalus debequaeus fruit by Georgia Doyle
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Taxonomic Comments

Weber and Wittmann (2012) note that this is regarded by some as a color form of Astragalus eastwoodiae.

Ranks and Status

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

[+] Description and Phenology

Please see 1997 profile

General description: Perennial plants forming multi-branched clumps, up to roughly 2 dm. in height.  Flowers are white or yellowish-white, mostly 7-9 (11) per raceme; calyx tubes have short black hairs and are 5-6 long.  Stems and pod are glabrous (Spackman et al. 1997, Ackerfield 2012).

Look Alikes: Astragalus eastwoodiae flowers are pink-purple, mostly 3-7 per raceme; and the calyx tubes are mostly 8-9 mm long (Ackerfield 2012).

Phenology: Astragalus debequaeus flowers April-May and produces fruit May-July (Colorado Natural Heritage Program 2013).

[+] Habitat

Habitat of Astragalus debequaeus by Terry Bridgman
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Habitat of Astragalus debequaeus by Susan Spackman Panjabi
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Astragalus debequaeus is found in varicolored, fine-textured, seleniferous, saline soils of the Atwell Gulch Member of the Wasatch Formation, in areas surrounded by pinyon-juniper woodlands and desert shrub.  Plants are mostly clustered on toe slopes and along drainages, but many occur on steep sideslopes. Soils are clayey but littered with sandstone fragments. Associated taxa include Achnatherum hymenoides, Artemisia tridentata ssp. wyomingensis, Astragalus flavus, Atriplex confertifolia, Atriplex gardneri, Cercocarpus montanus, Chrysothamnus depressus, Ephedra viridis, Gutierrezia sarothrae, Pediomelum megalanthum, Opuntia polyacantha, Physaria acutifolia, Platyschkuhria integrifolia, and Tetraneuris ivesiana (Welsh 1985, O'Kane 1986, Spackman et al. 1997, Colorado Natural Heritage Program 2014).

Elevation Range: 4,944 - 6,680 feet (1,507 - 2,036 meters)

[+] Distribution

Distribution of Astragalus debequaeus in Colorado.
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Colorado endemic: Yes
Global range: Colorado endemic, known from Delta, Garfield and Mesa counties, in the Colorado River Valley near DeBeque. The plant's range evidently corresponds to the extent of the Atwell Gulch Member of the Wasatch Formation. Estimated range is 1,736 square kilometers (670 square miles), calculated in 2008 by the Colorado Natural Heritage Program in GIS by drawing a minimum convex polygon around the known occurrences.

[+] Threats and Management Issues

Summary results of an analysis of the status of Astragalus debequaeus based on several ranking factors. This species was concluded to be “weakly conserved”. From Rondeau et al. 2011.
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Oil and gas development is considered to be the primary threat to the species at this time (Rondeau et al. 2011).
Many occurrences are on public land that will likely be developed for oil and gas. This species occurs near oil shale deposits and would be severely threatened (should oil shale development begin) from developments associated with oil shale extraction. Grazing is not a high threat for this species as it accumulates selenium and likely is not an important forage plant. However, trampling by cattle has been observed. The state noxious weed, Bromus tectorum is reported at many occurrences and should be monitored. Off-road vehicle use is also a potential threat.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Colorado Native Plant Society. 1989. Rare plants of Colorado. Rocky Mountain Nature Association, Colorado Native Plant Society, Estes Park, Colorado. 73 pp.
    • Cronquist A. 1989. Intermountain Flora Vascular Plants of the Intermountain West, USA. Vol. 3, Part B. New York Botanical Garden, Bronx, NY.
    • Dawson, C. 2009. Personal communication with Colorado Natural Heritage Program staff regarding BLM rare plant monitoring in Colorado.
    • Elliott, B. A., S. Spackman Panjabi, B. Kurzel, B. Neely, R. Rondeau, M. Ewing. 2009. Recommended Best Management Practices for Plants of Concern. Practices developed to reduce the impacts of oil and gas development activities to plants of concern. Unpublished report prepared by the Rare Plant Conservation Initiative for the National Fish and Wildlife Foundation.
    • Jennings, W. 1990. Field surveys.
    • 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.
    • O'Kane, S. L. 1988. Noteworthy Collections, Colorado. Madrono, 35(4):353-359.
    • O'Kane, S.L. 1986. Field Surveys.
    • 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.
    • Scheck, C. 1994. Special Status Plants Handbook Glenwood Springs Resource Area. Unpublished report prepared for the Bureau of Land Management, Glenwood Springs, CO.
    • Spackman, S., B. Jennings, J. Coles, C. Dawson, M. Minton, A. Kratz, and C. Spurrier. 1997. 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.
    • U.S. Fish and Wildlife Service (USFWS). 2007. Endangered and Threatened Wildlife and Plants; 90-Day Finding on A Petition to List Astragalus debequaeus (DeBeque milkvetch) as Threatened or Endangered. Federal Register 72(30): 6998-7005.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • 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. 1985. A new species of Astragalus (Leguminosae) from Mesa County, Colorado. Great Basin Naturalist 45 (1):31-33.
    • Welsh, S.L. 2007. North American Species of Astragalus Linnaeus (Leguminosae) A Taxonomic Revision. Brigham Young University, Provo, Utah. 932 pp.

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