Mat Buckwheat - Eriogonum caespitosum
State Rank Reason (see State Rank above)
Rare in Montana, where it is has been documented from a few sites from Beaverhead County. Trends are unknown, though the potential for negative impacts to known populations appears to be low.
Mat Buckwheat is a low, perennial herb or subshrub that forms cushions up to 5 cm high. The alternate, oblong leaves are 10-15 mm long, including the petiole, have entire, downturned margins, and persist on the stem after withering. The foliage is covered with long, gray hairs. The numerous flowers are borne in crowded, globose inflorescences atop leafless stalks that are 3-8 cm high. Flowers arise from a solitary, cup-shaped involucre with 6-7 reflexed lobes. Each flower has 6 yellow and rose, petal-like perianth segment that are 3-5 mm long. The perianth segments are united below and taper to a hairy woolly base.
Flowering in June.
The tapered, stalk-like perianth and the solitary involucre distinguish this species from other mat-forming Erigonum.
Southeast OR to CA, east to central ID, MT, WY, and CO.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Dry, stony limestone sagebrush steppe.
Ecological Systems Associated with this Species
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus bifarius
, Bombus centralis
, Bombus flavifrons
, Bombus huntii
, Bombus melanopygus
, Bombus mixtus
, Bombus ternarius
, Bombus occidentalis
, Bombus insularis
, and Bombus flavidus
(Thorp et al. 1983, Koch et al. 2012, Williams et al. 2014).
Threats or Limiting Factors
STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
- Literature Cited AboveLegend: View Online Publication
- Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
- Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
- Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ: Princeton University Press. 208 p.
- Additional ReferencesLegend: View Online Publication
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- Lesica, P. and J. Vanderhorst. 1995. Sensitive plant survey of the Sage Creek area, Beaverhead County, Montana, Dillon Resource Area, Bureau of Land Management. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program. 36 pp. plus appendices.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
- Rundquist, V.M. 1973. Avian ecology on stock ponds in two vegetational types in north-central Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 112 p.
- Vanderhorst, J.P. and P. Lesica. 1995a. Sensitive plant survey of the Tendoy Mountains in the Beaverhead National Forest, Beaverhead County, Montana. Unpublished report to the Bureau of Land Management, Butte District. Montana Natural Heritage Program, Helena, MT. 59 pp. plus appendices.