Native Range

Europe

Appearance

Orange hawkweed is an upright perennial forb typically growing up to 2 ft tall (60 cm) from a fibrous root system with short rhizomes and stolons. Orange hawkweed stolons are reddish-maroon, grow up to 12 inches long, and form daughter rosettes at their tips. Once daughter plants root, the stolons die, and the new plant becomes independent. Stems are largely unbranched until the tips. Leaves are lance-shaped, up to 6 in (15 cm) long, and typically occur only in a basal rosette, though one or two smaller leaves may occur midway up the plant stem. Stems and leaves are covered with stiff hairs that can be simple, glandular, and/or star-shaped. Leaves and stems contain a milky latex. Flower heads are ≤1 in (2½ cm) in diameter with an average of 30 orangish-red florets. Seed head bracts are covered in hairs. Seeds small and brown and are topped by tufts of pappus, resembling dandelion seeds.

Impact

Exotic invasive hawkweeds reduce forage and crop production and displace native plant species in natural areas. Some species have demonstrated allelopathy where they release compounds into the soil that inhibit the growth of other plant species. Orange hawkweed is allelopathic in that its pollen interferes with the reproduction of other plant species.

Reference

Moffat, C.E., De Clerck-Floate, R.A., J. Littlefield, and G. Cortat. 2023. Hawkweeds (Pilosella spp.): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2023-36- HAWKWEEDS-P. https://bugwoodcloud.org/resource/files/29156.pdf

Selected Images

Maps

Invasive Listing Sources

• Alaska Noxious Weeds
• Alberta Weed Control Act
• California Invasive Plant Council
• Colorado Noxious Weeds
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Idaho Noxious Weeds
• Invasive Plant Association of Wisconsin
• Invasive Plant Species of West Virginia
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• Montana Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• New Invaders of the Southeast
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Oregon Noxious Weeds
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999

References