Arctic Sweet Coltsfoot - Petasites frigidus var. frigidus
State Rank Reason (see State Rank above)
Rare in Montana, where it is at the southern edge of its range. Known from a few widely scattered sites in the northwest corner of the state.
Arctic sweet coltsfoot is a rhizomatous, perennial herb with erect stems that are 1-3 dm high and clothed in alternate, overlapping, brownish parallel-veined bracts that are 25-60 mm long. Leaves arise from the ground separately and later than stems. Blades are up to 2 dm wide and are spade-shaped with lobed margins and long petioles. Leaves are glabrous above but covered with long white hairs beneath. Many stalked flower heads are borne in a small umbrella-shaped inflorescence at the top of the stem. Each head is 5-9 mm high and has a single series of involucral bracts surrounding the white tubular flowers. Some heads have flowers with fertile ovaries and inconspicuous rays but without stamens. Other heads have flowers without rays but with fertile stamens and sterile ovaries. The achenes are topped by numerous unbranched, white bristles, which form a pappus.
Flowering in late May - early June.
The more common var. sagittatus has leaves that are merely toothed on the margins.
AK to NL south to CA, CO, SD, WI and NY (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
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)
Swamps, fen margins, and riparian seeps within open forest and meadows in the valley and foothill zones.
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 sylvicola
(Thorp et al. 1983, Williams et al. 2014).
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana's populations of Arctic Sweet Coltsfoot refer to expected impacts to populations along roads and trails (MTNHP Threat Assessment 2021). Populations along roads are potentially easily destroyed by road maintenance. One population is intersected by a hiking trail where it is exposed to trampling and has been damaged by trail maintenance in the past. Concern for the genetic resilience of another population is indicated where evidence of hybridization with Petasites sagittatus is found.
- Literature Cited AboveLegend: View Online Publication
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 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. 1991. Noteworthy Collections in Montana....
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.