Astragalus iodopetalus
Author: (Rydb.) Barneby

Violet milkvetch

Fabaceae (Pea Family)

Close up of Astragalus iodopetalus by Teresa Burkert
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Close up of Astragalus iodopetalus by Teresa Burkert
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Ranks and Status

Global rank: G2
State rank: S1
Federal protection status: USFS Sensitive
State protection status: None

[+] Description and Phenology

Astragalus iodopetalus by Teresa Burkert
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Astragalus iodopetalusby Teresa Burkert
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General description: Astragalus iodopetalus is a perennial legume that grows to 10 to 20 cm tall and has reddish violet flowers that are 18-23 mm long.  The leaves are pinnate with 8-15 elliptic to ovate leaflets (5-15 mm long) that are variably pubescent. Its crescent-shaped pods are about 20-30 mm long, and glabrous (Harrington 1979, Weber and Wittmann 2012, pers. comm. Burkert 2012). 

Look Alikes: No look-alikes have been noted for this species. Available habitat descriptions do not include any other species of Astragalus.

Phenology: Flowers in late May and June (Colorado Natural Heritage Program 2012).

[+] Herbarium Photos

Images of Astragalus iodopetalus housed at the Colorado State University Herbarium.

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[+] Habitat

Habitat of Astragalus iodopetalus by Teresa Burkert
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This species occurs on dry stony hillsides and benches, commonly on granite, often about oak thickets, in the pinyon-juniper and ponderosa pine zones, in oak-pinyon forests, or among sagebrush (Barneby 1964). Weber and Wittmann (2012) report that this species is found in sagebrush habitat in Colorado.

Elevation Range: 6,512 - 7,264 feet (1,985 - 2,214 meters)

[+] Distribution

Distribution of Astragalus iodopetalus in Colorado according to mapped land ownership/management boundaries (CNHP 2012, COMaP v9 ).
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Distribution of Astragalus iodopetalus in Colorado
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Colorado endemic: No
Global range: Known from New Mexico and Colorado (Archuleta, Gunnison, La Plata and Montrose counties).

State range: Known from Archuleta, Gunnison, La Plata and Montrose counties in Colorado. Estimated range in Colorado is 7204 square kilometers (2782 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 New Mexico.

[+] Threats and Management Issues

Summary results of an analysis of the status of Astragalus iodopetalus 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 recreation/hiking (Rondeau et al. 2011). It is not known if all of the occurrences are or are not threatened by these activities. The most well documented occurrence is within the Chimney Rock Archaeological Area, and may be threatened there by recreationists.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
    • Colorado Natural Heritage Program. 2008. The Fifth Annual Colorado Rare Plant Symposium: G2 Plants of Colorado. Symposium Minutes. Available on-line
    • Colorado Natural Heritage Program. 2012. Biodiversity Tracking and Conservation System. Colorado State University, Fort Collins, CO.
    • Colorado State University Herbarium. 1999. "Colorado State University Herbarium Database". database.html. (May 15 1999).
    • Harrington, H. D. 1964. Manual of the plants of Colorado. Sage Books, Swallow Press, Chicago. Second edition. 666 pp.
    • Harrington, H.D. 1954. Manual of the plants of Colorado. Sage Press, Chicago. 666 pp.
    • Harrington, Harold D. 1979. Manual of the Plants of Colorado. Reprinted for Grove Press by University Microfilms International, Ann Arbor Michigan.
    • Heil, K.D., S.L. O'Kane Jr., L.M. Reeves, and A. Clifford, 2013. Flora of the Four Corners Region, Vascular Plants of the San Juan River Drainage; Arizona, Colorado, New Mexico, and Utah. Missouri Botanical Garden Press, St. Louis, Missouri. 1098 pp.
    • Kartesz, J., and the Biota of North America Program (BONAP). 1998. A Synonymized Checklist of the Vascular Flora of the United States, Puerto Rico, and the Virgin Islands.
    • 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.
    • 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.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • USDI United States Geological Survey. 2003. National Assessment of Oil and Gas Project - San Juan Basin Province (022) Boundary. Vector digital data. U.S. Geological Survey, Central Eneergy Resources Team. Denver, CO.
    • 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.
    • Weber, W.A., and R.C. Wittmann. 1996a. Colorado flora: Eastern slope. Revised edition. Univ. Press of Colorado, Niwot, Colorado. 524 pp.
    • 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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