: Petasites officinalis, Petasites vulgaris
: Pestilence wort, Butterfly-dock
: Introduced to North America for its medicinal uses. Shown to be effective in reducing the severity of migraine headaches.
: Erect, upright, perennial, spineless, grows to 2 ft in height.
: Simple, basal, roundish and somewhat heart-shaped or kidney-shaped, 1-2 ft in diameter, grow on 3-4 ft tall stems, petioles long and hollow with ridges, margins irregularly toothed, smooth above and wooly below.
: Upright, leaf scales, reproductive, flowering stem can be circular or with lots of small angles, no leaves above the base, hairy.
: Pink to purple in color, disk (tabulate) florets arranged in dense spike on a 5-20 cm thick stalk, 11-20 flowers but could have up to 50, dioecious with male and female on separate plants, appear before foliage emerges, main bracts are oblanceolate to oblong; blooms in early spring.
Fruit and seeds
: Flowers give way to a fruit in the form of an achene, up to 3mm in length with a smooth, fine hairy pappus.
: Native to Europe. Found in disturbed sites, meadows, fields or shores of rivers and lakes.
: By seed or rhizomes.
: Native Arctic sweet coltsfoot (Petasites frigidus var. palmatus
Monitoring and rapid response
: Initial infestations may be controlled by hand-pulling to remove the entire plant. Can be effectively controlled using any of several readily available general use herbicides such as glyphosate.
: The information provided in this factsheet was gathered from University of Massachusetts Amherst and the New England Wild Flower Society.
Individual species images that appear with a number in a black box are courtesy of the Bugwood.org network (http://www.invasive.org).Individual photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (http://images.google.com).