By Scout Nelson
Thistle species, including biennial types like bull and musk thistle and the perennial Canada thistle, are starting to bud across South Dakota. This is a key time for action, as the plants begin to produce seeds. Herbicides are not effective during this budding stage, so clipping or mowing is the best way to manage them now.
Farmers and landowners should clip or mow these plants before they produce seeds. Once seeds develop, mowing can help spread them, making the problem worse. If seeds are already forming, it’s better to cut off the flower heads, bag them carefully, and destroy them. Though this method takes more effort, it prevents more thistles from growing later.
Monitoring the fields after cutting is important. These weeds can grow back quickly in just a few months. For long-term control, applying herbicide in the fall is often more effective. Fall is when thistle plants send sugars down to their roots to store energy for winter. Applying herbicide currently ensures it travels deep into the plant, reaching the roots and rhizomes for better control.
To use herbicides properly, follow label directions and check SDSU Extension’s latest “Weed Control: Noxious Weeds” guide. Also, wait for the first frost if you plan to spray, as this is the most effective window for managing perennial weeds like Canada thistle.
Photo Credit: south-dakota-state-university
Categories: South Dakota, Education, Harvesting, Rural Lifestyle