How to Control Bull Thistle
- 1). Install a grass catcher onto a lawn mower, using the manufacturer's instructions and set the deck height to between 1 and 2 inches above the ground. Mow the entire area of bull thistle growth.
- 2). Remove the grass catcher and empty the clippings into a trash bag. Place the trash bag into the garbage for disposal. Do not empty the clippings in another area of the yard or your compost pile, since they may contain bull thistle seeds that can sprout.
- 3). Repeat mowing on a regular basis, or at least once more during the growing season to prevent flowers from developing on any bull thistle regrowth.
- 4). Wait until mid to late fall and locate the bull thistle rosettes on the ground. The rosettes look like large leaves that are low to the ground and branch out from a center root.
- 5). Spray the rosettes with an herbicide containing Picloram. Mix the herbicide with water as instructed and place it in a garden sprayer. Saturate each bull thistle plant with the herbicide until it drips off the leaves.
