War on Weeds — Weeds are Everybody’s Problem

Orange Hawkweed

Orange hawkweed (Hieracium auantiacum) is a perennial weed native to Europe. It was originally introduced to the U.S. as an ornamental, its bright orange-red flowers probably made it irresistible to some horticulturists. It has proven to be a dangerous weed because of its ability to spread by seed, stolons and rhizomes. This weed invades meadows, pastures and roadsides across the country.

Orange hawkweed forms a basal rosette of oblong shaped leaves, a single leafless stem extends out of the rosette. Clusters of rosettes are often formed as stolons and rhizomes spread. Stems are usually about 12 inches tall, are covered in small hairs and ooze milky latex when severed. Each stem bares a cluster of bright orange-red flowers. Flowers are typically 1/2-3/4 inch in diameter, the petals are square and notched. A single flower can produce 12-30 seeds, seeds can remain viable for approximately seven years. Seeds are easily dispersed by wind and water.

Integrated Pest Management (IPM) options

• Prevention — Learn to identify this plant. Always plant clean seed, this weed is sometimes a contaminate in wildflower seed packets.
• Mechanical — Tillage or digging is not recommended. Broken rhizomes and stolons will resprout, causing the infestation to worsen. Mowing is not effective, as it encourages this weed to produce rhizomes and stolons.
• Cultural — Establish a stand of desirable plants to compete with orange hawkweed.
• Chemical — Non-selective herbicides are not generally recommended for the control of this weed unless desirable species are planted to compete with orange hawkweed. Apply selective herbicides prior to flowering and in the fall before the first frost. For specific information on appropriate herbicide active ingredients visit https://pnwhandbooks.org/weed and then search “Hawkweed, Orange.”

Idaho is a wonderful place with awesome natural resources, landscapes, agriculture and recreational opportunities. Weeds threaten all the things that we love about Idaho. To detect, contain and control weeds in Idaho we have declared “War on Weeds.” These short articles are designed to give a brief description of each species, an explanation about why it’s a problem, insights into identification and Integrated Pest Management control options. — Justin Hatch

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• Orange hawkweed, 5-11