How Fast Will Thistles Regrow After Cutting?

Revenge of the Rosette

• Cutting thistles at the rosette stage actually encourages more vigorous growth. During the rosette stage, the thistle has a taproot with leaves growing in a low cluster around it. If the thistle is cut back at this stage, it begins to regrow within a few days. The thistle will send up more growth nodes, increasing the number of flowers that may develop later on. Cutting a thistle frequently at this stage, for example with a lawnmower, may also result in the flowers being produced close to the ground, making it harder to remove them before they go to seed. Removing the taproot is more effective than cutting a thistle at the rosette stage.

At the Bolting Line

• When the thistle sends up a stalk it is bolting, or getting ready to produce seeds. If a stalk is cut before the flower is produced, it will regrow, but may take a few weeks to do so. The amount of time it will take to regrow depends on the variety of thistle. While it is tempting to cut the thistle as soon as it bolts, waiting longer will decrease the chance that the thistle will grow back.

Fragile Flower

• The best time to cut a thistle to keep it from growing back is as the flower is forming, but not yet open. At this stage, most thistles will not grow back if they are cut down. It is important to cut the thistle back before the flower develops, however. If the thistle develops seeds, cutting it down may aid in spreading the seeds, making the infestation worse.

The Root of the Problem

• Thistles are either biannual or perennial. They have strong roots that will survive underground even after the top has been cut back. Repeatedly cutting thistles back will prevent the root from storing energy. If the roots are deprived of enough energy, they will lose the ability to send up new shoots and die. New seedlings are more vulnerable than established thistles. Removing the entire taproot of a seedling is the best way to get rid of thistles.