Montana Field Guide

Idaho Fleabane is a small perennial herb that is 2-20 cm tall. It has 1 to a few stems arising from a slender taproot. The basal leaves are up to 10 cm long, and have a broadly lance-shaped to nearly round blade and a long petiole. The few stem leaves are smaller and reduced upwards. The herbage is densely covered with short spreading hairs. The daisy-like, flowering heads are solitary (or, occasionally, there are 2) at the ends of the stalks. The involucral bracts are 5-9 mm long and covered with glands and spreading hairs. The 10-25 deep blue or violet rays that compose the petals of the flowering head are 5-10 mm long. The disk corollas in the center of the head are 4-6 mm long. The achenes have 20-30 bristles, forming a pappus, at their tops.

Flowering occurs in July-August.

There are many species of high-elevation, low-growing, taprooted Erigeron, and it is difficult to distinguish among them. Erigeron evermannii and E. leiomerus have glabrous leaves. Hair on the stems of E. tweedyi and E. tener is appressed rather than spreading outward. The larger leaves of E. caespitosus have three nerves, while those of E. asperugineus have only one. Leaves of E. radicatus, E. ochroleucus and E. rydbergii are nearly linear; the petiole not distinguishable from the blade.

The species typically grows on windswept, rocky or gravelly slopes and ridges in alpine zones, often on limestone-derived soils. Associates that have been documented at Montana sites include Agropyron spicatum (dominant with cushion plants at one locality), Haplopappus acaulis, Phlox mulitflora, Arenaria congesta, Erigeron compositus, Senecio canus, Bupleurum americanum and Antennaria umbrinella.

Erigeron asperugineus is a low-growing plant, easily shaded by taller plants. It always occurs in sparse vegetation. One collection (possibly misidentified) from the 1960's referred to its habitat as "overgrazed."

POLLINATORS
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 huntii, Bombus melanopygus, Bombus mixtus, Bombus rufocinctus, Bombus occidentalis, and Bombus insularis (Thorp et al. 1983, Wilson et al. 2010, Colla and Dumesh 2010, Koch et al. 2012).

The alpine habitat of E. asperugineus is at low risk from anthropogenic disturbance; however there are very few recent records, so it is difficult to make inferences about its status.

STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).