Orange Hawkweed, Hieracium aurantiacum, is relatively new in the Swan Valley but it is spreading rapidly. This member of the sunflower family has 5-30 showy orange blossoms near the top of 1-3-foot tall stems. The leaves are narrow and spatula-shaped and most of the leaves are in the basal rosettes. The stems have bristly hairs and the entire plant contains a milky juice. Orange hawkweed has more than one method of spreading. Its seed heads are like tiny dandelion puffs that sail on the wind. The plants also form mats that cover large areas and crowd out all other vegetation. Unlike knapweed, orange hawkweed can thrive under the tree canopy or out in the open.

Orange Hawkweed Prevention and Treatment
Orange hawkweed should be eradicated as soon as it is located and before it forms large patches. Learning to identify and map orange hawkweed is critical. Unlike knapweed, hawkweeds in the Swan Valley are still in small enough patches that the plants can be eradicated. Orange hawkweed should be destroyed before logging or conducting other activities involving heavy equipment. Orange hawkweed will accelerate its spread in the disturbed soil. Clipping the seed heads can slow the plant's spread, but it is not sufficient to eradicate the weed. If only a few plants are found, they can be dug up and destroyed. The site should be revisited for several years to be sure all the plants were removed. Hawkweeds are hard to recognize after the blossoms go to seed. Early summer is the time to look for hawkweeds in the Swan Valley.

Once orange hawkweed is widespread, spraying with herbicides is the only effective option we know of. Herbicides should be applied by a trained applicator at the rates recommended by the product manufacturer. The best time to apply herbicides is when the plants are vigorously growing, usually in May, June or early July.

Any effective treatment should include re-vegetation with native plants or other desirable vegetation.

For more information visit Missoula County Weed District.