Astragalus sparsiflorus
Author: Gray


Front Range milkvetch


Fabaceae (Pea Family)

Close up of Astragalus sparsiflorus by Pamela Smith.
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Close up of Astragalus sparsiflorus by Rich Scully.
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Close up of Astragalus sparsiflorus by Pamela Smith.
Click image to enlarge.
Close up of Astragalus sparsiflorus by Rich Scully.
Click image to enlarge.

Taxonomic Comments

Ackerfield (2015) recognizes two varieties, var. majusculus and var. sparsiflorus, based on differences in the leaflets of upper leaves, calyx tubes, and fruit, noting that they are sometimes found at the same locality. Weber and Wittmann (2012) mention the same, emphasizing the difference in pod size with var. sparsiflorus smaller, and less than 1 cm long. Both varieties are endemic to Colorado (USDA, NRCS 2016).

Ranks and Status

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

[+] Description and Phenology

No artwork available.

General description: Perennial, prostrate to decumbent, 0.5-3.5 dm tall. Leaves pinnately compound with 9-17 leaflets.  Inflorescence 2-9 flowered (sparsiflorus=few flowered), calyx tube with mixed black and white hairs. Flowers whitish with a spotted or blotched keel. Pods are up to 2.5 cm long (less than 1 cm in var. sparsiflorus), three angled, mottled, and covered with small, sharp, appressed hairs (Ackerfield 2015).
 

Look Alikes: Could be confused with A. tenellus, but the leaves are very different from that species. Could also be confused with Astragalus alpinus when it is not in fruit (pers. comm. Pam Smith, CNHP, 2017).

Phenology:

[+] Herbarium Photos

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

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Click image to enlarge.

[+] Habitat

Habitat of Astragalus sparsiflorus by Rich Scully.
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Habitat of Astragalus sparsiflorus by Rich Scully.
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Habitat of Astragalus sparsiflorus by Rich Scully.
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Evergreen forests, dry gravelly banks, meadows, open hillsides and sandy canyon bottoms, sometimes on road cuts or natural talus (Barneby 1964, Ackerfield 2015).  Some associated species inlcude: Pinus ponderosa, Populus tremuloides, Pseudotsuga menziesii, Muhlenbergia montana, Phacelia heterophylla, Heterotheca villosa, Verbascum thapsus, Artemisia frigida, Aliciella pinnatifida, Chondrosum gracile.

Elevation Range: 5,469 - 9,970 feet (1,667 - 3,039 meters)

[+] Distribution

Distribution of Astragalus sparsiflorus in Colorado according to mapped land ownership/management boundaries (CNHP 2017, COMaP).
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Distribution of Astragalus sparsiflorus in Colorado.
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Colorado endemic: Yes
Global range: Colorado endemic: Boulder, Custer, Douglas, El Paso, Fremont, Jefferson, Park, and Teller counties. 

[+] Threats and Management Issues

Recreation (hiking, biking, and fishing) is the primary threat to this species. Colorado climate scenarios for 2050 suggest temperature will increase by 3-7 F and precipitation may decrease or increase. The impact to any given rare plant habitat is likely to vary. Long-term monitoring that includes weather and soil moisture data is critical to understanding climate impacts.

[+] References

    • Ackerfield, J. 2015. Flora of Colorado. Brit Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.
    • Colorado Natural Heritage Program and the Geospatial Centroid. 2017. The Colorado Ownership and Protection Map (COMaP). Colorado State University, Ft. Collins, CO.
    • 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.
    • USDA, Natural Resources Conservation Service, PLANTS Database [USDA PLANTS]. http://plants.usda.gov/. Accessed 2017.
    • USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

Last Updated

2017-01-12