War on Weeds—weeds are everybody’s problem
Photo courtesy of John Cardina, The Ohio State University, Bugwood.org
THE ISSUE: Yellow devil hawkweed
Yellow devil hawkweed (Hieracium glomeratum) is a perennial wildflower native to Europe. It invades disturbed areas, roadways, pastures, grasslands, and other sites. It is very competitive allowing it to take over areas that once belonged to beneficial native species that provided good forage to livestock and wildlife.
Yellow devil hawkweed has stems that can grow up to 2 feet tall, originating from rosettes. Stems are leafless, but they have blackish bristly hairs. Rosette leaves are about 7 inches long, have stiff bristly hair on the underside, and are smooth on the top. Its bright yellow ray flowers look like dandelion flowers. Multiple flowers are often produced on each stem. It reproduces by seed that float for long distances on the wind. Interestingly, its pollen is allelopathic, meaning that it contains toxins that discourage other plants from growing by preventing seed germination and seedling growth.
Integrated Pest Management (IPM) Options:
• Prevention— Learn to identify this plant. Never transport unknown plant material. Always plant clean seed!
• Mechanical— Hand digging or pulling can be effective on small infestations. Remove as much of the roots as possible. Tillage is not recommended because it can reproduce from rhizomes, allowing it to spread.
• Cultural— Establish a healthy stand of beneficial plants that will compete for essential resources. Nitrogen applications can help grasses out compete yellow devil hawkweed.
• Chemical—Glyphosate is a non-selective herbicide that can effectively control this weed, but it will also kill other beneficial plants. When trying to preserve beneficial grasses consider using 2, 4-D + Dicamba, or Aminopyralid. Always read and follow herbicide label directions!
Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou and Bear Lake Counties. 208-547-3205 [email protected]
