Thistles are categorized as weeds simply because they can be an unwanted plant. One of the main reasons people do not want thistles on their property is because they contain sharp prickles that can hurt when you brush up against them. There are a few items you probably have in your house that will control the thistles for you. You can use this formula to kill some or all of the thistles.
Dump the salt into a bucket. If you don't have a small bucket, you can use an empty milk jug. Salt is well known for its ability to kill any type of plant, including thistles.
Add vinegar to the bucket and stir until the salt has dissolved. Vinegar breaks down the cell membranes of the thistle's plant tissue.
Drip in your liquid dish soap. The dish soap helps the other two ingredients stick to the thistle when sprayed. That makes the solution more effective.
Place your homemade thistle killer in an empty spray bottle and spray the thistles you want to kill. If you want to keep a few thistles, do not spray those.
Sprinkle cornmeal on the ground once your thistles die. Cornmeal will keep new thistles from growing in the future.