10 Ways to Get Rid of Canadian Thistles (Permanently)

Co-authored by Ben Barkan and Hannah Madden

Last Updated: May 30, 2024

Canadian thistle is notorious for its spiky leaves, purple flowers, and rapid growth rate. The fluffy seeds that grow in the spring are light enough to catch on the wind, so the thistle can spread rapidly, taking over entire habitats in the blink of an eye. If you have Canadian thistle in your area, you may need to spend multiple seasons trying different management techniques to get rid of it completely. Prevention and early treatment are key, so don’t wait!

1

Spray herbicide on the infestation.

Download Article

It’s the most effective way to kill Canadian thistle. Start by spraying a broadleaf herbicide on the thistle patch in the early spring before it has a chance to flower. Follow up with a second application in the late fall to kill the roots.
- Look for an herbicide with aminopyralid, glyphosate, or chlorsulfuron on the ingredients list.
- Herbicides are dangerous chemicals, and they can cause irritation. Always read the warning label on your bottle of herbicide, and wear gloves and eye protection to stay safe.

2

Pull the thistle by hand if it isn’t flowering.

Download Article

Make sure you get the entire root system out as you pull. If the thistle isn’t flowering, put on a pair of gloves and gently tug the entire plant upward by the stem. ^{[1]
X
Expert Source

Ben Barkan
Garden & Landscape Designer

Expert Interview. 14 April 2020.} If the thistle is flowering, pulling it out will only spread the seeds, so you should pick a different method.
- If you pull the thistle and it doesn’t have any flowers on it, you can throw the stems in with your compost pile or yard debris bin.
- If you accidentally pull a thistle that has flowers on it, bag it and take it away to be burned. Flowering thistles can spread seeds even if they aren’t in the ground.

3

Mow the thistle with a lawn mower.

Download Article

Large infestations will need multiple mows to get them under control. ^{[2]
X
Expert Source

Ben Barkan
Garden & Landscape Designer

Expert Interview. 14 April 2020.} Do an initial mow in late June to catch the thistle before it starts flowering. As the thistle regrows, you’ll have to mow it again throughout the late summer to keep it from spreading seeds. ^{[3]
X
Research source}
- After using your mower on thistle, inspect it carefully and clean it off. If there are any seeds stuck to your mower, bag them and burn them.

4

Introduce goats to graze if the thistle is young.

Download Article

Goats can eat the seedlings and help thin the infestation. Try to bring the goats in during early spring before the seeds start to spread. They’ll chomp the seedlings down and keep them from flowering. ^{[4]
X
Expert Source

Ben Barkan
Garden & Landscape Designer

Expert Interview. 14 April 2020.}
- Like mowing, you may have to allow your animals to graze multiple times throughout the year to keep the thistle from flowering.
- Goats are the most effective at grazing, but sheep, cattle, horses, donkeys, and llamas will also eat it.

5

Till the soil.

Download Article

Deep tilling will destroy the thistle’s roots. Use a hoe to till the soil at least 4 in (10 cm) deep and remove the majority of the thistle. This works best on young plants that aren’t flowering yet, so try this out on young, thin patches. ^{[5]
X
Research source}
- It’s important to till as far down as you can. Shallow tilling will actually encourage the spread of Canadian thistle.
- On its own, tilling isn’t a very effective method. It works best when you follow up with an herbicide application.

6

Thin the thistle out with a prescribed burn.

Download Article

Large patches might need to be thinned before you can tackle them. Contact a local fire team in your area to come out and set fire to the thistle patch. Follow up a few months later with a second controlled burn if you need to. ^{[6]
X
Research source}
- Controlled burns don’t work very well on their own. They’re most effective when you follow up with an herbicide application.
- Never try to do a controlled burn on your own without the supervision of a professional.

7

Check hay and straw for weed seeds.

Download Article

With Canadian thistle, prevention is key. If you purchase hay and straw, make sure it’s certifiably weed-seed free before you bring it onto your property. If you aren’t sure, check the bales and make sure you aren’t introducing Canadian thistle (or any other weeds) into the area.
- Canadian thistle seeds are brown and only about 1 mm (0.039 in) wide. They can be hard to distinguish from other seeds, so if you spot any seeds at all in your hay or straw, don’t bring it onto your property.

8

Plant perennial grasses in barren areas.

Download Article

Canadian thistle grows easily in barren patches of land. If you have an area on your property that’s mostly dirt, throw some grass seeds down and let them take root. The thistle will have a harder time rooting and growing in an area that already has plants in it.
- Try planting switchgrass, fountain grass, or reedgrass.

9

Release weevils and beetles in the area.

Download Article

There are a few species of insects that will eat Canadian thistle. Cassida rubiginosa, Rhinocyllus conicus, Trichosirocalus horridus , and Urophora cardui are all natural predators of Canadian thistle. However, you need to get a permit through the US Department of Agriculture before you use this method. Once you get your permit, the USDA can point you in the direction of a seller.
- Some species of insects might be more suited for areas than others. It’s important to get a permit and check with your local laws before using a biological control method.

10

Report Canadian thistle to your local government.

Download Article

They can help you come up with the best strategy for removal. They might even be able to give you a grant or assistance. If you’re out and about and happen to see it, tell them exactly where it is so they can go out and treat it.
- Once Canadian thistle is established, it’s really hard to get rid of. Prevention and early treatment are key.

Expert Q&A

Search

Add New Question

Question

How do you kill Canadian thistle naturally?

Tyler Radford
Plant Specialist
Tyler Radford is a Plant Specialist at Hollie’s Farm & Garden in Tampa, Florida. With over nine years of experience, Tyler specializes in gardening, planting, mulching, and potting. Hollie’s Farm & Garden is a full-service landscape nursery offering landscape supplies including trees, shrubs, mulch, and flagstone.

Tyler Radford

Plant Specialist

Expert Answer

For a natural alternative, try using a vinegar-based weed spray to kill your Canadian thistles.

Thanks! We're glad this was helpful.
Thank you for your feedback.
If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
Yes No

Not Helpful 1 Helpful 15

Ask a Question

200 characters left

Include your email address to get a message when this question is answered.

Submit

Tips

Most of these methods work best if you use them in conjunction with each other.

Thanks
Helpful 0 Not Helpful 0

Submit a Tip

All tip submissions are carefully reviewed before being published

Name

Please provide your name and last initial

Submit

Thanks for submitting a tip for review!

Warnings

In some areas, it is illegal not to report Canadian thistle if you spot it.

Thanks
Helpful 0 Not Helpful 0

[1]

Expert Source

Ben Barkan
Garden & Landscape Designer

[2]

[3]

[4]

[5]

[6]

Log in

10 Ways to Get Rid of Canadian Thistles (Permanently)

Steps

Spray herbicide on the infestation.

Pull the thistle by hand if it isn’t flowering.

Mow the thistle with a lawn mower.

Introduce goats to graze if the thistle is young.

Till the soil.

Thin the thistle out with a prescribed burn.

Check hay and straw for weed seeds.

Plant perennial grasses in barren areas.

Release weevils and beetles in the area.

Report Canadian thistle to your local government.

Expert Q&A

Tips

Warnings

You Might Also Like

References

About This Article

Did this article help you?

Quizzes

You Might Also Like

Featured Articles

Trending Articles

Featured Articles

Featured Articles

Watch Articles

Trending Articles

Quizzes

Explore Categories