Thistles are strong and undesirable weeds that can spread easily and become a pest quickly in your yard or garden. Thistles are very competitive, and will choke out other plants in order to spread out more. Removing thistles can sometimes be difficult, especially when there is a large infestation of them involved. There are several treatments for removing thistle, but a combination of many methods may be needed to completely eradicate them.
Cut your grass very close to the ground, when the thistles are 4 to 6 inches long, and right before the winter. If you cut down the thistles when winter is coming, they will not have enough time to recover in most cases, and will freeze out when the cold weather comes. This works best with very large infestations of thistles that cover an entire yard.
Use a shovel to dig up each thistle plant and all of its roots. If there are just a few thistles mixed in throughout your flower garden or yard, it may be possible to get rid of them by simply digging up each of the thistles.
Introduce grazing animals--such as cows and goats--into the areas were the thistles exist. This only works if the thistles are found in your pastures and you want them eliminated, or want to keep them from spreading to your yard or garden.
Cover the thistles with pieces of plastic, heavy dark coloured fabric, or a tarp. Since thistles need sun to grown, introducing unending shade can quickly kill a thistle, but this only works well when there is only a small thistle problem, and you need to remember that the plastic or other material can also kill the grass that it is covering in your yard.
Bring in some thistle eating weevils or other bugs that only feed on and kill thistles, and let them destroy the thistles.
Spray the thistles with a weed killing spray. The only problem with this method is that it can also sometimes kill certain types of grass that it identifies as weeds, and it can be costly.
Burn the thistles in the yard as a last resort. If you have tried everything and still can't eliminate the thistles from your yard, you can try burning the yard and starting over with a clean slate. Proper safety measures should be taken to ensure that the fire is controlled, and looking into a professional service that safely handles property burning is advised.
Try using several methods together for better results when trying to eliminate thistles from your yard or garden.
Use caution when working with chemicals or fire to remove thistles.