Type of Weed: Broadleaf
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
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).
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).
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.