Thistle weeds can take over a yard quickly and one thistle plant can produce up to 20,000 seeds. Thistle weeds will steal nutrients from other plants and choke them out as they spread in your lawn. In agricultural settings, thistle weeds threaten grazing grasses and wheat. Once thistle seeds contact the soil, they can remain viable for up to seven years. Removing the thistle from your yard may require different methods to kill them successfully.
- Skill level:
Things you need
- Lawnmower or shears
- Systemic herbicide
- Thistle head weevil
- Garbage bags
Put on gloves, long sleeves and trousers. Cut the thistle plant at the soil level with a lawnmower or shears. Cut the weeds in the spring before the seeds develop. Continue to cut the thistle repeatedly as it regrows to weaken the roots to stop the weeds from growing.
Dig thistle weeds from the ground with a spade. Dig 12 inches away from the base of the thistle plant to create a circle around the base. Dig into the soil at an angle with a shovel and lift the plant from the soil. The root ball needs to remain attached to the plant. Remove any roots that remain in the ground with gloves so the weed does not grow in the same location again.
Spray a systemic herbicide to the thistle foliage in the spring after the buds appear or in the fall. The herbicide must contain clopyralid chlorsulfuron, glyphosate or dicamba. Allow the herbicide to remain on the thistle plant for up to 10 days. Repeat the application on plants that remain alive. Always follow the dosage instructions on the herbicide to apply it properly.
Introduce a thistle head weevil to the thistles in your yard. The weevil will eat the thistle and kill it. You can purchase these insects at most nurseries and speciality garden supply stores. The thistle head weevils must be purchased within your state from a distributor because you cannot transport them between states.
Collect the thistle debris in a garbage bag. Dispose of the thistle plant foliage immediately so that the seeds do not spread or blow across the lawn.
Tips and warnings
- Introduce grazing animals like sheep or cattle to large areas to remove the thistle.
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- National Sustainable Agriculture Information Service: Thistle Control Alternatives
- University of Minnesota Extension; Thistle Control; December 1999
- Purdue University Department of Botany: Control Practices for Canada Thistle
- University of Illinois Integrated Pest Management: The Bulletin Thistle Identification and Management; Aaron Hager et al.; April 2004