Astragalus equisolensis
Author: Barneby

Horseshoe milkvetch

Fabaceae (Pea Family)

Close up of Astragalus equisolensis by Peggy Lyon
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Close up of Astragalus equisolensis by Peggy Lyon
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Taxonomic Comments

Weber and Wittmann (2012) do not list A. equisolensis or A. desperatus var. neeseae. Ackerfield (2012) lists A. equisolensis as a synonym for A. desperatus var. neeseae.

Ranks and Status

Global rank: G5T1
State rank: S1
Federal protection status: BLM Sensitive
State protection status: None

[+] Description and Phenology

Astragalus equisolensis by Kaye Thorne
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General description: A perennial plant, 5-15 cm tall, with leafless flower stems and typical pea flowers. The wings and keel are purple, while the banner (large top petal) is bicolored--purple with white stripes.  Plants are pubescent.  Racemes are 4-13 flowered.  Pods are declined to deflexed, sessile or stipitate, obliquely ovoid or lance-ellipsoid, lunately curved, dorsiventrally compressed, constricted distally at the beak, laterally compressed, incurved, 10-14 mm long, 3.5-6.5 mm wide, hirsute, and unilocular (Welsh et al. 2003).

Look Alikes: Not likely to be confused with other Astragalus species as long as the distinctive flowers or fruit are present. Astragalus desperatus has flowers 7-10 mm long, while A. equisolensis flowers are 13-16 mm long (Ackerfield 2012).

Phenology: Flowers in late April and May, and fruit by the end of May (Colorado Natural Heritage Program 2012). Friuting may continue through mid-summer.

[+] Habitat

Habitat of Astragalus equisolensis by Peggy Lyon
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A. equisolensis is associated with mixed desert and salt desert shrub vegetation communities that are generally dominated by sagebrush, shadscale and horsebrush. The populations in Mesa County are in an open juniper/blackbrush community on rocky convex slopes with red soils. Often the plants are found growing under the blackbrush shrubs. Associated species include Juniperus osteosperma, Coleogyne ramosissima, Astragalus amphioxys, Eriogonum microthecum, Hymenopappus filifolius, Cryptantha flavoculata, Arabis pulchra, Cymopterus fendleri, Yucca angustissima, Castilleja scabrida, Cryptantha flava, Townsendia incana, Tetraneuris ivesiana, Aristida purpurea and Astragalus mollissimus.

Elevation Range: 4,518 - 6,027 feet (1,377 - 1,837 meters)

[+] Distribution

Distribution of Astragalus equisolensis in Colorado according to mapped land ownership/management boundaries (CNHP 2012, COMaP v9 ).
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Distribution of Astragalus equisolensis in Colorado
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Colorado endemic: No
Global range: One known population area in the vicinity of Horseshoe Bend of the Green River in the center of the Uinta Basin in Uintah Co., Utah. This taxon is also disjunct in nearby Mesa County, Colorado (Welsh et al. 2005).
State range: Known from Mesa County in Colorado.

[+] Threats and Management Issues

Summary results of an analysis of the status of Astragalus equisolensis based on several ranking factors. This species was concluded to be “Moderately Conserved”. From Rondeau et al. 2011.
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Road construction, road maintenance, motorized recreation, and non-motorized recreation are management concerns for this species. In the 2006 Candidate Notice of Review (USFWS 2006), the U.S. Fish and Wildlife Service found that listing this species was not warranted and removed it from the candidate list.

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • 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.
    • Colorado Natural Heritage Program. 2008. The Fifth Annual Colorado Rare Plant Symposium: G2 Plants of Colorado. Symposium Minutes. Available on-line
    • England, L. 2002. March 20-last update. Candidate and Listing Priority Assignment Form: Astragalus equisolensis. U.S. Fish and Wildlife Service, Endangered Species Program. Online. Available: Accessed 2003, February 7.
    • Harrington, H.D. 1954. Manual of the plants of Colorado. Sage Press, Chicago. 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.
    • Lavender, A.E., M.M. Fink, S.E. Linn, D.M. Theobald. 2011. Colorado Ownership, Management, and Protection v9 Database. Colorado Natural Heritage Program and Geospatial Centroid, Colorado State University, Fort Collins, CO. (30 September).
    • 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.
    • Panjabi, S., B. Neely and P. Lyon. 2011. Preliminary Conservation Action Plan for Rare Plants in the Gateway Priority Action Areas. Prepared by The Nature Conservancy and the Colorado Natural Heritage Program. Unpublished report prepared for the National Fish and Wildlife Foundation. 29 pp.
    • U.S. Fish and Wildlife Service (USFWS). 2004. Species assessment and listing priority assignment form. Astragalus equisolensis. 9 pp.
    • U.S. Fish and Wildlife Service (USFWS). 2006. Endangered and Threatened Wildlife and Plants; Review of Native Species That Are Candidates or Proposed for Listing as Endangered or Threatened; Annual Notice of Findings on Resubmitted Petitions; Annual Description of Progress on Listing Actions. Federal Register 71: 53756-53835.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Welsh, S.L. 2007. North American Species of Astragalus Linnaeus (Leguminosae) A Taxonomic Revision. Brigham Young University, Provo, Utah. 932 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.
    • 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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