Hieracium aurantiacum • Class B

The plant has a basal rosette of narrow, pointed leaves, which may be smooth or have bristles, but are not wooly underneath like the Mouse-ear hawkweed. Its leaves contain a milky sap. Orange hawkweed produces 5 to 30 compact, umbelliform flower heads that are bright red and orange in the center and stand from a few inches to 2 feet tall; they are leafless and covered with stiff hairs. 

Its creeping growth fills in the gaps between other plants forming mats of rosettes which prevents other plants from establishing seedlings. When conditions are ideal, one plant can spread and infest a 2 to 3 foot area in one years’ growth. 

Orange hawkweed infests wetlands and lawns and is especially invasive on poorer acidic soils. It is an aggressive competitor for pastures, meadows, native grasslands. It prefers full to partial sunlight. It is unpalatable and crowds out more palatable species. 

Orange hawkweed is one of only 6 known Pollen Allelopathic plants. The pollen released from its flowers releases toxins that inhibit the seed germination, seedling emergence, and sporophytic growth of surrounding plants. 

As usual with invasive species, the best control measure for Orange Hawkweed is prevention. Early detection and eradication are vital to prevent the spread of hawkweed. It continues to be introduced in wildflower seed mixtures. Carefully review the ingredients of wildflower mixes to avoid accidental introduction. 

• For small infestations, manual removal can help control hawkweeds. Prevent seed production by removing plants that are budded or blooming. Bag all plant materials and dispose of them in the garbage, do not compost. 

• Treatment with nitrogen will help the grasses to competitively suppress hawkweed growth. 

• Early season treatment with 2, 4 D plus dicamba (as in Weedmaster, etc.) can be effective in controlling orange hawkweed. 

• Spot spraying with an herbicide containing the active ingredient glyphosate (Roundup Pro, Glyfos, etc.) may be used effectively in the spring while the plant is in the pre-bud to early bud growth stage. The goal is to insure all plants have emerged. Spray each plant thoroughly on the stems and leaves, enough to be wet but not dripping. Be aware, glyphosate is non-selective and will injure any plants that it comes in contact with, including grass. 

• For selective control of hawkweed in agricultural settings (pastures, hayfields, etc.): an herbicide containing the active ingredient aminopyralid (example: Milestone, Milestone VM, etc.) may be applied in the spring to plants in the pre-bud to early bud growth stage, it is also effective in the fall before a killing frost. Aminopyralid products will not harm grass and can be used around livestock (provided all label precautions are followed).  

• When using herbicides, always read and follow all label instructions and obey all label precautions. (Note: pesticide product registration is renewed annually and product names and formulations may vary from year to year.)  

• There are no known biological control agents for use on hawkweeds in the United States.  

 Download our Flyer or visit Washington State Noxious Weed Control Board Here. Photo by Leo Michels