ARROWLEAF COLTSFOOT

Petasites sagittatus (Banks) Gray

STATUS

USFS Region 1: Sensitive

USFWS: none

ICDC: G5/S3

INPS: Monitor

TAXONOMY

Family: Asteraceae (aster family)

Common Name: arrowleaf coltsfoot

Synonyms: Petasites dentatus

Description Petasites sagittatus is a tall (10-50 cm), rhizomatous forb with large leaves that open with or shortly after the flowers. Floristically it is very similar to Petasites frigidus palmatus , with the significant differences being vegetative. There are several flowering heads that are 5-9 mm high and formed in a corymbiform to racemiform inflorescence. The flowers are generally whitish, but can also be purplish or pinkish. The bloom lasts from April to June. The stem has several parallel veined bracts that decline upward. These are slightly longer and narrower than those of P. frigidus. The leaves are long-petioled and glabrous to sparsely hairy with a few erect hairs on the upper surface but densely hairy below. The large leaves can exceed 30 cm in length and are cordate or more commonly sagittate. The leaf margins are dentate with 20-45 teeth on each side (Hitchcock 1955).

Distinguishing Features and Similar Species Before the large basal leaves emerge, arrowleaf coltsfoot is very similar to sweet coltsfoot and the two are not readily distinguished. Arrowleaf coltsfoot has slightly longer and narrower bracts on the stem. It also is more limited to swampy meadows, while sweet coltsfoot often grows along streambanks and moist woods in addition to moist meadows. The best way to tell these two species apart is to wait until the large basal leaves emerge. The leaves of sweet coltsfoot are palmate, while those of arrowleaf coltsfoot are strongly sagittate or arrowhead shaped.

DISTRIBUTION

Range Arrowleaf coltsfoot is circumboreal in distribution, extending from Alaska to Labrador, south to northeast Washington, north Idaho, Montana and Colorado (Hitchcock 1955). In Idaho it occurs mainly in Bonner and Boundary Counties. In Idaho County, it occurs on the Clearwater National Forest near Powell. This occurrence extends the Idaho range approximately 160 miles to the south. However, the Powell population would be more closely linked to populations occurring south of Lolo in the Bitterroot Valley of Montana (Lackschewitz 1991). It is quite possible that this species occurs in other meadows in the vicinity of Powell.

Habitat Arrowleaf coltsfoot occurs in wet meadows that are usually saturated or submerged in early spring. Along the Bitterroot River it often is found in willow or alder thickets (Lackschewitz 1991). The Powell location is in a wet meadow dominated by sedges and alder. The plants are found throughout the small meadow, but perhaps most dense along the margins of the alder.

REMARKS

This species possibly occurs in other wet meadows in the Powell vicinity. Its large leaves are very distinct, however it is most noticeable in April and May when the flowering stalks are in full bloom. The tall, thick stems with large, dense flowering clusters are a stark contrast to the brown, dead vegetation of the meadow at such an early season. The extremely early phenology of this species may cause it to go undiscovered, since patches of late snow may hinder access to many of the meadows.

REFERENCES

Hitchcock, C.L., A. Cronquist, M. Ownbey, and J.W. Thompson. 1955. Vascular Plants of the Pacific Northwest. Part 5. University of Washington Press, Seattle, WA.

Lackschewitz, K. 1991. Vascular Plants of West-Central Montana. Identification Guidebook. General Technical Report INT-277. Intermountain Research Station, Ogden Utah.