Guide to Thistle Identification & Control

Thistle broadleaf weed

Type of Weed: Broadleaf

Cirsium Vulgare


Bull thistle is a spring-to-summer biennial weed, with a taproot system once mature. It commonly grows in unmanaged spaces like pastures, ditches, and roadsides.

This weed can rapidly spread close to 5,000 seeds a season that can be distributed by animals, clothing, equipment, wind, etc. (which can be an issue for neighboring gardeners or lawns).

In its first year, bull thistle forms a rosette of leaves and in its second year produces a flowering stem.

How to Identify

Bull thistles rosette stage consists of long, jagged prickly green leaves that can grow up to 7 inches long and 2 feet across. In its bolting stage it will produce green, hairy erect stems with several pink, purple, and sometimes white domed single head flowers (with spines at its base).

These flowers bloom during the summer. Bull thistle can grow up to 6 feet tall and its flowers are 1-3 inches in diameter. The colored flower will eventually turn to a white, feathery tuft enabling seed distribution (similar to a dandelion).

Control Methods

Control Difficulty: Moderate to Difficult

For thistle weeds in the rosette stage, manually pulling them up (ensuring to remove the taproot from below the soils surface), or spraying with selective pre-emergent herbicide is most effective.

For thistle that is in the bolting stage, mowing will prevent the weed from being able to continue growing and eventually blooming. However, once bloomed, clipping the flower (and carefully disposing in a trash bag), will help prevent the number of seeds that can release.

You may also use a selective post-emergent herbicide after mowing or clipping thistle. For flower beds or natural areas that are invaded with thistle, providing shade over the weed can help kill it off.

After manual control, plant densely around the weed so that new plants can take over and shade out any new thistle trying to grow, or cover the area with a thick layer of mulch (about three inches high).

Prevention Tips

Having a dense, thick lawn is an easy way to deter weeds from popping up or taking over. By mowing your lawn at the proper height, having proper aeration, fertilization, and irrigation, can all result in a healthy lawn.

Proper use of a selective pre and post emergent herbicide can keep thistle at bay if you find it starting to invade your lawn or garden.

If you continue to have issues with bull thistle, our team of expert technicians are ready to help you get your lawn back under control.
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