Little Sunflower -
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Helianthus pumilus is documented from a single 2007 collection from Big Horn County, Montana (Rocky Mountain Herbarium #910246). It was previously reported for Montana by the Flora of the Great Plains (McGregor et al. 1986). Globally this plant occurs in Colorado and Wyoming where it occupies dry, rocky places (Schilling in Flora of North America 2007). This location, though imprecisely mapped, extends the range northward. Surveys that bring forth precise mapping and data on population sizes, habitat, and threats are greatly needed.
Plants: Stems are rough-hairy, simple or branched, and up to one meter tall from a tough, tap-rooted crown (McGregor et al. 1986). Leaves: Leaves are opposite with distinct petioles, which are 0.4 to 3 centimeters long (McGregor et al. 1986; eFloras 2017). Blades are ashy green and egg- or lance-shaped with tapering bases and entire to serrate margins (McGregor et al. 1986). Dimensions are 4 to 15 centimeters long by 1 to 4 centimeters wide (McGregor et al. 1986). The leaves are stiffly hairy and dotted with glands (eFloras 2017). Inflorescence: There are few radiate heads on short peduncles (McGregor et al. 1986). There are 15 to 25 loosely clasping involucral bracts, 3.5 to 7.5 millimeters long (eFloras 2017). Like the leaves, they have glands as well as stiff, whitish hairs (eFloras 2017).
Flowers July to August (McGregor et al. 1986).
Colorado and Wyoming (eFloras 2017).
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)
Found in dry, open areas with rocky soil at the base of the Rocky Mountains (eFloras 2017; McGregor et al. 1986).
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap:
(Thorp et al. 1983, Mayer et al. 2000, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014).
Flowers: The disk is yellow or sometimes reddish and 1 to 1.5 centimeters across, surrounded by about 10 yellow ray flowers. Each disk flower is subtended by an entire or three-lobed chaffy bract, which is 7 to 8 millimeters long (McGregor et al. 1986; eFloras 2017).
Fruit: Achenes are 3 to 4 millimeters long, with awn-like and triangular pappus scales that are soon deciduous (McGregor et al. 1986; eFloras 2017).
Threats or Limiting Factors
STATE THREAT SCORE REASON Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
Literature Cited Above
Legend: View Online Publication Colla, S., L. Richardson, and P. Williams. 2011. Bumble bees of the eastern United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 103 p. Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68. eFloras. 2017. Flora of North America. Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA. Hazlett, D. 2007. Helianthus pumilus 12693. Accession number 910246. In Rocky Mountain Herbarium (RM). Laramie: University of Wyoming. Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p. Mayer, D.F., E.R. Miliczky, B.F. Finnigan, and C.A. Johnson. 2000. The bee fauna (Hymenoptera: Apoidea) of southeastern Washington. Journal of the Entomological Society of British Columbia 97: 25-31. McGregor, R.L. (coordinator), T.M. Barkley, R.E. Brooks, and E.K. Schofield (eds). 1986. Flora of the Great Plains: Great Plains Flora Association. Lawrence, KS: Univ. Press Kansas. 1392 pp. 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.