Linear-leaved Willowherb - Epilobium palustre var. gracile
MNPS Threat Rank
See species description.
Erect perennial herbs, often robust and rank, spreading by threadlike, nearly leafless epigeous stolons that terminate in compact fleshy turions. Stems erect, terete, 15-95 cm tall, simple to well branched in larger plants, covered throughout with dense incurved strigillose hairs, sometimes mixed with glandular ones on the inflorescence, lacking decurrent lines from the leaf bases. Leaves linear to very narrowly elliptic, 2-7.5 cm long, 0.15-0.7 cm wide, not much reduced in size on inflorescence, usually longer than internodes, densely strigillose-pubescent both sides, increasing up stem, sometimes revolute, subacute especially in upper pairs, subentire with inconspicuous lateral veins, subsessile, occasinally fascicled. Inflorescence erect, crowded, leafy. Flowers erect; floral tube 0.8-1.5 mm long, 1.2-1.8 mm wide, densely strigillose outside, with a ring of spreading hairs inside at the mouth; sepals 2.5-4.5 mm long, 0.9-1.3 mm wide, green, strigillose; petals 3.5-7 mm long, 1.6-4 mm wide, white to light pink, obcordate with apical notch 1-1.8 mm deep; anthers 0.6-0.9 mm wide, cream, filaments white or cream, unequal, 0.8-3.5 mm long, at least the longer stamens usually shedding pollen directly onto stigma; ovaries 12-18 mm long, densely white canescent, rarely with an admixture of gland-tipped hairs, on pedicels 5-12 mm long, style 2-3.8 mm long, deep cream, stigma cream, narrowly clavate, rarely exserted beyond stamens. Capsules 3.5-8 cm long, slender, canescent, on pedicels 1.5-3.5 cm long; seeds 1.5-2.2 mm long, 0.5-0.7 mm wide, attenuate, narrowly obovoid, densely papillose, chalazal collar sometimes quite pronounced, 0.2 mm or less long, coma (tuft of hairs) 6-8 mm long, dingy white, persistent (Hoch 1986, in Flora of the Great Plains).
Hoch's description is based on recognition of this taxon as a species, not subspecies.
Widespread across much of North America excluding the southeast (Kartesz 2009).
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)
Marshes, seepage areas, and mesic disturbed sites (Hoch 1986).
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 fervidus
, Bombus flavifrons
, Bombus frigidus
, Bombus melanopygus
, Bombus mixtus
, Bombus rufocinctus
, Bombus sylvicola
, Bombus ternarius
, Bombus sitkensis
, Bombus occidentalis
, Bombus griseocollis
, Bombus impatiens
, Bombus insularis
, Bombus suckleyi
, and Bombus kirbiellus
(Thorp et al. 1983, Mayer et al. 2000, Colla and Dumesh 2010, Wilson et al. 2010, Colla et al. 2011, Koch and Strange 2012, Koch et al. 2012, Pyke et al. 2012, Williams et al. 2014).
- Literature Cited AboveLegend: 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.
- Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
- Koch, J.B. and J.P. Strange. 2012. The status of Bombus occidentalis and B. moderatus in Alaska with special focus on Nosema bombi incidence. Northwest Science 86: 212-220.
- 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.
- Pyke, G.H., D.W. Inouye, and J.D. Thomson. 2012. Local geographic distributions of bumble bees near Crested Butte, Colorado: competition and community structure revisited. Environmental Entomology 41(6): 1332-1349.
- 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.
- Wilson, J.S., L.E. Wilson, L.D. Loftis, and T. Griswold. 2010. The montane bee fauna of north central Washington, USA, with floral associations. Western North American Naturalist 70(2): 198-207.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.