How to get rid of thistle in your yard
How to get rid of thistle depends on which thistle you have. Canada thistle spreads through creeping roots, so you wear it down by cutting it every two to three weeks and treating it with a systemic herbicide in late summer or fall. Bull and musk thistle live only two years and spread by seed, so you kill them by cutting the root below the crown while they are low rosettes and never letting them flower.
Contents
Which thistle do you have?
Look at how the plants grow, the stems and the size of the flower heads. If your weed has spines but none of these traits, check our weed identification guide.
| Canada (creeping) thistle | Bull thistle | Musk thistle | |
|---|---|---|---|
| Life cycle | Perennial, creeping roots | Biennial, taproot | Biennial, taproot |
| How it grows | Dense patches of many stems, 1 to 4 feet tall | Single plants, 2 to 6 feet tall | Single, branched plants, 2 to 8 feet tall |
| Stems | Smooth, no spiny wings | Spiny wings along the upper stem | Spiny wings along the stem |
| Leaves | Variable: wavy, lobed, spiny edges | Deeply lobed, each lobe tipped with a sharp spine | Deeply lobed, often with silvery-white edges |
| Flower heads | Small (about 1 inch), many per plant, pink-purple to white, no spines on the bracts | Large (2 to 3 inches), gumdrop-shaped, purple | Large (2 to 3 inches wide), deep rose to violet, nodding |
Native thistles, such as tall thistle and field thistle, have leaves with white, woolly undersides. They are part of the local flora and valued by pollinators, so leave them alone unless they are in your way. Canada, bull and musk thistle, on the other hand, are on the noxious weed lists of a number of states; check your state’s list to know your obligations.
Protect your hands: wear thick leather or coated gloves, long sleeves and long pants. Thistle spines go straight through thin garden gloves.
How do you get rid of Canada thistle?
Canada thistle, also called creeping thistle, is a perennial whose deep roots spread sideways and send up new shoots, so one plant becomes a patch. Root pieces as small as half an inch can grow into a new plant. Pulling and digging snap the roots and leave most of them behind, and tilling cuts them into pieces that each sprout. The strategy is the same as for bindweed: exhaust the roots, then finish them off with a well-timed systemic herbicide where that is an option.
- Cut every two to three weeksFrom spring until frost, cut every stem at ground level with sharp shears or a mower. Each new set of leaves costs the roots stored food; the shoots get weaker over time. Never let the patch flower.
- Smother small patchesCut the stems, then cover with cardboard or landscape fabric plus 5 to 6 inches of mulch, extending past the patch. In hot weather, clear plastic left for four to six weeks heats the soil enough to kill shallow roots, though deep roots may survive. Check the edges for shoots. Our mulch for weeds guide covers materials.
- Spray in late summer or fallFrom late summer into fall, the plant sends food down to its roots for winter, and a systemic herbicide goes with it. Treat the leafy regrowth after your summer cutting. If you spray only once a year, this is the time.
- Or spray in spring, before buds openOnce most shoots have come up and before flower buds open, a spring treatment also helps; it is less effective on the roots than a fall one.
- Repeat for yearsTreat any regrowth the following season. Total eradication usually takes two to three years or more of steady effort.
Which herbicides kill Canada thistle?
| Where | Active ingredients | Notes |
|---|---|---|
| Lawns | Combinations of 2,4-D, dicamba, MCPA, triclopyr, fluroxypyr | Selective broadleaf weed killers: kill thistles, spare grass. Repeat applications are usually needed. |
| Beds, fence lines, bare ground | Glyphosate | Kills any plant it touches. Spot-spray or wipe it onto the thistle leaves only. |
| Pastures, rangeland, non-crop areas | Clopyralid, aminopyralid | Very effective on thistles, but restricted on most home sites (see warning below). |
Warning about clopyralid and aminopyralid: these persist in treated grass clippings, in hay, and in manure from animals that ate treated forage, then in compost, sometimes for years. Tiny amounts damage tomatoes, peppers, potatoes, beans, peas, lettuce, roses and many other garden plants. Since 2002, its manufacturer has restricted clopyralid lawn uses to non-residential turf. Use them only where the product label explicitly allows, and never compost clippings or manure from treated areas.
Read and follow every label: it lists the weeds controlled, the rate, the grass types it is safe on and the re-entry time for pets and children. In the US, the label is the law.
How do you get rid of bull and musk thistle?
Bull thistle and musk thistle are biennials. In their first year, they grow as a flat rosette of spiny leaves and store food in a taproot. In the second year, they send up a tall flowering stalk, set seed and die. They spread only by seed, and a single musk thistle averages around 50 flower heads, each with several hundred seeds. So the whole game is to kill rosettes and stop seed.
- Dig out rosettesPush a sharp spade or weeding fork into the soil next to the rosette and cut the taproot a few inches below the crown (the point where leaves meet the root). Removing the crown is what counts: if it stays, it can sprout again.
- Spray rosettes in fall or early springBiennial thistles are much easier to kill as rosettes, in fall of their first year or in early spring before the stalk shoots up. In lawns, a broadleaf product containing 2,4-D works on rosettes.
- Cut flowering plants before they bloomIf a plant has already bolted, cut it at the base just before the flowers open. Buds in the crown often resprout, so check again in a few weeks.
- Bag the flower headsFlower heads that have started to open can still ripen seed after cutting. Put them in a sealed bag in the trash, not on the compost or the ground.
Mowing a field of bull or musk thistle does little to the rosettes, which sit below the blades. Time the mowing for just before flowering, and plan on at least two mowings during the summer to stop all seed.
How do you keep thistles out of your yard?
- Keep the lawn thick. Thistle seedlings struggle in the shade of dense grass. Mow at the right height for your grass type and overseed thin spots; see our lawn weeds guide.
- Cover bare soil. Beds with plants or mulch give windblown seeds nowhere to start.
- Check soil and mulch you bring in. Canada thistle root pieces travel in topsoil and fill.
- Edge your beds. A deep edge slows creeping roots moving in from the lawn or a neighbor’s lot.
- Remove every flower. One season of seed feeds years of seedlings.
Common thistle mistakes
- Pulling Canada thistle by hand and thinking it is gone: the roots stay and resprout.
- Tilling a thistle patch, which spreads root pieces through the bed.
- Spraying a Canada thistle patch once in June and stopping.
- Mowing bull thistle rosettes and expecting them to die.
- Composting clippings from a lawn treated with a persistent herbicide.
- Killing native thistles that were doing no harm.
FAQ
What kills thistles permanently?
For Canada thistle, a systemic herbicide applied in late summer or fall, when the plant moves food down to its roots, combined with cutting every two to three weeks during the season. Expect two to three years or more. For bull and musk thistle, which live only two years, cutting the taproot below the crown or spraying the rosette in fall or early spring kills the plant; the job is then to stop new seeds.
What kills thistle but not grass?
Selective broadleaf lawn herbicides. Products combining ingredients such as 2,4-D, dicamba, MCPA, triclopyr or fluroxypyr control thistles without killing lawn grasses when used as labeled. Apply them to actively growing thistles, ideally in late summer or fall for Canada thistle.
Should you pull thistles?
Pulling bull or musk thistle rosettes works if the root comes out below the crown; a weeding fork or shovel does it better than your hands. Pulling Canada thistle mostly snaps the stems off and leaves the creeping roots, which resprout. Wear thick gloves either way.
Does mowing kill thistles?
Not by itself. Mowing does little to bull and musk thistle rosettes, which sit below the blade, but mowing just before they flower, and again when they regrow, stops seed production. Mowing a Canada thistle patch once or twice a year gives it time to regrow; frequent mowing or cutting every two to three weeks is what wears down the roots.
Is creeping thistle the same as Canada thistle?
Yes. Creeping thistle is another common name for Canada thistle (Cirsium arvense), which comes from Europe and Asia despite its name. The name describes its creeping root system, which spreads sideways and sends up new shoots to form patches.
When is the best time to kill thistles?
For Canada thistle, late summer to fall is the most effective time for herbicides, with a second chance in spring before the flower buds open. For bull and musk thistle, target the rosette stage: in fall of the first year or early spring of the second, before the flower stalk shoots up.
Related
- Weed identificationWeed identification made simple: grass, broadleaf or sedge, leaf shape, flowers and growth habit. Use the free weed identifier, then get the fix for each weed.
- Broadleaf weed killerBroadleaf weed killer explained: how 2,4-D, MCPP, dicamba and triclopyr kill weeds but not grass, the best fall timing, and how to avoid drift and tree damage.
- BindweedHow to get rid of bindweed for good: tell field and hedge bindweed from morning glory, cut it back on a schedule, time the herbicide and never till it in.
- Lawn weedsCommon lawn weeds by type (grassy, broadleaf, sedge), what each one says about your lawn, and the right control and timing to get rid of weeds in grass.
- Mulch for weedsMulch for weeds works when it is 2 to 3 inches deep over weeded soil and kept off stems. Compare mulch types, sheet mulching and when to top it up.
Updated October 3, 2026