Astragalus tortipes
Author: J. L. Anderson & J. M. Porter

Sleeping Ute milkvetch

Fabaceae (Pea Family)

Ranks and Status

Global rank: G1
State rank: S1
Federal protection status: BLM Sensitive, USFWS Candidate
State protection status: None

[+] Description and Phenology

General description: A robust perennial herb, 3-8 dm tall,with 1-6 sparsely leafy, ascending to erect, stems, which are purplish at the base. Plants are ashy-gray (cinereous) and white-hairy (strigose) throughout. Flowers are yellow. There are 9-15 leaflets per leaf. Seed pods are glabrous, laterally compressed, and borne erect or ascending; they are green at first, then turn maroon-mottled. When the plants are in fruit the pedicels become twisted, causing the pods to be erect (Spackman et al. 1997).

Look Alikes: Astragalus tortipes is distinguished from other Astragalus species by the hyper-twisting of pedicels, which causes the pods to be erect (Spackman et al. 1997). 

Phenology: This plant flowers from April through June. The phenological cycle in A. tortipes is evidently of short duration. The entire raceme of an individual plant proceeds from flower to fruit within a two week period. By the end of June the plants have died back to the ground and only the dried stalks of the inflorescences are present (Anderson and Porter 1994).

[+] Habitat

This species is found on lower slopes of ridges and knolls, in gravels derived from a volcanic intrusion into Mancos Shale (Spackman et al. 1997). In mixed desert scrub with Atriplex confertifolia, Chrysothamnus greenei, Eriogonum clavellatum, Frankenia jamesii and Gutierrezia sarothrae (Anderson and Porter 1994). Associated with the white zone of the Upper Cliff House Sandstone (Floyd and Colyer 2003).

Elevation Range: 5,449 - 5,689 feet (1,661 - 1,734 meters)

[+] Distribution

Colorado endemic: Yes
Global range: Colorado endemic (Ute Mountain Ute Reservation, Montezuma County). Estimated range is 10 square kilometers (4 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

Motorized recreation is considered to be the primary threat to the species (Rondeau et al. 2011). Off-road vehicle impacts are becoming severe in some areas. A borrow pit at the northeastern-most corner of the range on an isolated hill is currently receiving vehicle traffic but the milkvetch is reproducing around the edges (Colyer 2000). An irrigation canal carrying McPhee Reservoir water to the Ute Farms runs along the northwestern edge of the milkvetch range. Three hills were cut through and some of the population was undoubtedly removed. The remaining adjacent stands of milkvetch are stable (Colyer 2000). Cattle grazing and prairie dogs do not appear to negatively impact the milkvetch (Colyer 2000). 

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Anderson, J.L., and J.M. Porter. 1994. Astragalus tortipes (Fabaceae), a new species from desert badlands in southwestern Colorado and its phylogenetic relationships within Astragalus. Systematic Botany 19(1): 116-125.
    • Baskin, C.C., J.M. Baskin and E. Quarterman. 1972. Observations on the ecology of Astragalus tennesseensis. Amer. Midl. Natur. 88(1): 167-182.
    • Colorado Natural Heritage Program. 2004. The First Annual Colorado Rare Plant Symposium: Threatened, Endangered and Candidate Plants of Colorado. Symposium Minutes.
    • Colyer, M. 2000. Status Report of Sleeping Ute Milkvetch, Astragalus tortipes. Unpublished report prepared for the USFWS.
    • Floyd, M. L., and M. Colyer. 2003. Beneath the Trees: Shrub, Herbs and Some Surprising Rarities. Pages 31-60 in: L. M. Floyd, ed. Ancient Pinyon-Juniper Woodlands. University Press of Colorado, Boulder, CO.
    • Green, T.W. and G.E. Bohart. 1975. The pollination ecology of Astragalus cibarius and Astragalus utahensis (Leguminosae). Amer. J. Bot. 62(4): 370-386.
    • Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Monte L. Bean Life Science Museum, Brigham Young University; MLBM Press, Provo, Utah. 1007 pp.
    • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
    • Mayo, E. 2005. October-last update. Species assessment and listing priority assignment form: Astragalus tortipes. U.S. Fish and Wildlife Service, Endangered Species Program. Online. Available: (accessed 24 August 2007).
    • 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.
    • O'Kane, S.L. 1988. Colorado's rare flora. Great Basin Naturalist 48(4): 434-484.
    • 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. 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). 2004. Species assessment and listing priority assignment form. Astragalus tortipes. 8 pp.
    • U.S. Fish and Wildlife Service. 2015. 12-Month Findings on Petitions To List 19 Species as Endangered or Threatened Species. Federal Register 80(195): 60834-60850.
    • 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.

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