Astragalus naturitensis
Author: Payson

Naturita milkvetch

Fabaceae (Pea Family)

Close up of Astragalus naturitensis by Terry Bridgman.
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Close up of Astragalus naturitensis by Terry Bridgman.
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Ranks and Status

Global rank: G2G3
State rank: S2S3
Federal protection status: BLM Sensitive
State protection status: None

[+] Description and Phenology

Astragalus naturitensis by Irma Sturgell.
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General description: Naturita milkvetch is a white and purple flowered perennial, growing from a basal rosette of leaves. The plants have extremely small pinnate leaves with tiny gray-green leaflets that tend to fold in half, showing their lighter-colored undersides. The pods are red-mottled, firm-walled, and dorsiventrally compressed.

Look Alikes: Species similar to Astragalus naturitensis include: Astragalus deterior which is distinguished by its yellowish white flowers, and Astragalus desperatus which has smaller flowers, a shallower calyx-tube, and a loosely hirsute pod of broader and shorter outline (Barneby 1964). Astragalus monumentalis is similar but has firm-walled dorsiventrally compressed, essentially unilocular pods (Cronquist 1989). 

Phenology: Flowers April through early June, fruits in late May through early June (Colorado Natural Heritage Program 2012).

[+] Habitat

Habitat for Astragalus naturitensis by Peggy Lyon.
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Astragalus naturitensis occurs on sandstone ledges, crevices of sandstone bedrock, dry rock mesas, ledges, and detrital slopes (Harrington 1954). This species is found in pinyon-juniper woodlands in areas with shallow soils over exposed bedrock (Peterson 1981). Usually it is in small soil pockets or rock crevices in sandstone pavement along canyon rims. Sometimes it is found nearby in depper sandy soils with or without soil. Dominant plant community: Pinus edulis/Juniperus osteosperma. Associated plant species: Castilleja chromosa, Delphinium scaposum, Artemisia nova, Physaria acutifolia, Purshia tridentata, Oreocarya suffruiticosa. 

Elevation Range: 4,829 - 7,027 feet (1,472 - 2,142 meters)

[+] Distribution

Distribution of Astragalus naturitensis in Colorado according to mapped land ownership/management boundaries (CNHP 2015, COMaP v9). USFS is less than 1%.
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Distribution of Astragalus naturitensis in Colorado.
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Colorado endemic: No
Global range: Known from New Mexico, Utah, the Navajo Nation and Colorado.
State range: Known from Garfield, Mesa, Montezuma, Montrose and San Miguel counties in Colorado. Estimated range in Colorado is 10,640 square kilometers (4108 square miles), calculated in GIS in 2008 by the Colorado Natural Heritage Program by drawing a minimum convex polygon around the known occurrences. Also known from New Mexico, Utah, and the Navajo Nation.

[+] Threats and Management Issues

Summary results of an analysis of the status of Astragalus naturitensis based on several ranking factors. This species was concluded to be “Moderately Conserved”. From Rondeau et al. 2011.
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The primary threat at this time is considered to be oil and gas drilling (Rondeau et al. 2011). It is not known if all of the occurrences are or are not threatened by these activities. The habitat of the plant (primarily sandstone mesas, ledges, and crevices) may afford the plant some natural protection. Two sites reported as disturbed by moderate to severe grazing/trampling. One population is threatened by roadside activity and one reported "limited disturbance by seismic exploration."

[+] References

    • Ackerfield, J. 2015. Flora of Colorado. Brit Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.
    • Barneby, R. C. 1964. Atlas of North American Astragalus. Memoirs of New York Botanical Garden, vol. 13. New York Botanical Garden, Bronx, NY.
    • Barneby, R.C. 1989. Fabales. In A. Cronquist, A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren (eds.). Intermountain flora: Vascular plants of the Intermountain West, U.S.A. Vol. 3, Part B. New York Botanical Garden, Bronx. 279 pp.
    • Cronquist A. 1989. Intermountain Flora Vascular Plants of the Intermountain West, USA. Vol. 3, Part B. New York Botanical Garden, Bronx, NY.
    • Harrington, H. D. 1954. Manual of the Plants of Colorado. Sage Books, Denver, CO. 666 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.
    • Navajo Fish and Wildlife Department. 1995. Endangered species list for Navajo nation. [Effective 24 July 1995]. Navajo Fish and Wildlife Department, Window Rock, Arizona.
    • 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.
    • New Mexico Native Plant Protection Advisory Committee. 1984. A handbook of rare and endemic plants of New Mexico. Univ. New Mexico Press, Albuquerque. 291 pp.
    • Peterson, J. S. 1981. Status Report for Astragalus naturitensis. Unpublished report for the Colorado Natural Areas Program, Denver, CO.
    • 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.
    • Schneider, A. 2013. Wildflowers, Ferns, and Trees of the Four Corners Regions of Colorado, New Mexico, Arizona, and Utah. Accessed on-line at
    • 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.
    • USDA, NRCS. 2015. 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., N.D. Atwood, S. Goodrich and L.C. Higgins. (Eds.) 2003. A Utah Flora. 3rd edition. Brigham Young University, Provo, Utah, U.S.A. 912 pp.

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