Learn about Canada Thistle control so you can get rid of this weed without chemicals.

If you live on country acreage, you may be familiar with Canada thistle, an invasive weed that grows in many parts of Canada and the US. Thistles offer deep spreading roots with wind-borne seeds that can turn a whole lawn or pasture into a thorny battleground!

We’ve been successful in controlling it over time, due to the natural dislike I have for the plant and therefore, my willingness to work my plan to get rid of Canada thistle naturally, organically, here on our property.

Whether you have hay fields or are looking for Canada thistle control in lawns in your yard, here are solutions to help you get rid of thistle for good. Infestations can occur quickly in lawns and even in pastures. 

Thistles have a quick seed production, and they create new shoots quickly, so you can go from a little to a lot quickly.

Canada Thistle and Scotch Thistle Control

Both Canada Thistle and Scotch Thistle love to grow along our roadsides, and since the wind does carry the seeds, we will likely always have a few plants here in our fields. But, we know how to get rid of it. So if you’re wondering how to get rid of Canadian thistles easily, fast, and organically, read on.

I have found a couple of ways to get rid of a lot of it. And every year, my workload becomes lighter because there are fewer Canada thistle seedling coming up! Mowing doesn’t attack the root system, so if you want to say goodbye to the buds popping up, follow my system.

We also have Scotch thistle here, another invasive plant. These plants are much thicker and larger than Canada thistle. They both like to grow on soil that has been disturbed, such as road sides, logging roads, burned off areas, etc.

And, for the fertility of your soil and hayfields, thistles need to be removed permanently so that the grasses will benefit and grow. Of course, you can use chemicals to get rid of thistles and any other kind of weeds, however, chemicals are something we don’t want here. 

We find natural organic ways to get rid of weeds; improving the soil always helps as then the grasses grow so well they literally crowd out the weeds.

Canada Thistle Control

I have learned two main ways to get rid of Canada thistle weed, and I want to share both of them, but first, a few points about the plant itself.

Canada thistle (scientific name is Cirsium arvense) is a perennial plant, belonging to the Asteraceae family of plants. It grows in thick patches, spreading by its creeping roots. A very noxious weed that is found a lot in North America. Some areas see a lot in spring, late June, July,  August, and more of the hotter months of the year. So having an effective control plan is essential in controlling them.

Canada Thistle Identification 

What does Canada thistle look like? The plant can grow up to 7 feet but is often found at shorter heights. It has green leaves with sharp spiny edges and can be hairy on the underside of the leaves. 

It is very easy to spot this weed when it is flowering! The Canada thistle flower is like a purple pompom, which really helps when it comes to searching for this weed in fields. The flowers stand out like, well, sore thumbs.

Scotch Thistle Identification

Scotch Thistle is also known as Cotton Thistle. It is a large plant, thick and tall, topping out at about 10 feet. It has a grey green colour and sharp thorns along the stem. If you’ve got these growing, you’ll see them!

I use the same eradication methods to get rid of Scotch Thistle as I do Canada Thistle.

Why is Canada Thistle Bad?

You want to get rid of all Canada Thistle plants in your garden, acreage and fields. Canada Thistle is on the list of noxious plants in the province of BC. 

Since this thistle is an invasive species, it can do damage to fields over time. Alfalfa fields are known for the spread. They love the shade, vegetation, and thrive. This can also bring unwanted insects like weevils into the crop. Not only will it compete (and eventually win) against the grass you seeded, Canada Thistle also seriously depletes the soil of nutrients.

This is counterproductive especially when it comes to fields planted with wheat and other grains. It is undesirable in hay fields as well.

Should I pull Canada thistle?

While you can pull the plants, I will share more ways to control the regrowth and spread of this exotic species. 

Late spring or early summer is the time of year when you will find that pulling a Canada thistle offers the best return for removing the plant. Some things to know about the foliage is that you need to wear thick gloves as they have a lot of spines on them that poke. 

These plants have an extensive root system, so making sure you dig at least 6-8 inches down or deeper is going to help reduce the chance of reproduction. 

Make sure to bag and throw away all that you dig up, as any fluff, flowers, and such can cause more spreading and growth of a new parent plant. Do not compost the buds or seeds. This helps with the control of Canada thistle.

Canada Thistle Control: Cutting Thistle Plants

The first control method for eradicating Canada Thistle or Scotch Thistle is by cutting the plant down. This method works very well, especially if some of the flower pods have begun setting seeds.

I do not bother to hunt down small thistle plants for cutting. It is far easier to wait until the plant is actually in flower! I do this for a couple of reasons:

• It is much easier to spot the plants when they are in flower! The bright purple blooms really stand out, and it is very easy to find the plants for cutting down.
• I like to wait until the plant has spent a lot of its energy into flowering. A plant’s natural desire is to flower so it can then set seed, thereby reproducing to “make babies” the next year. So, I wait until the plant is putting everything it has into flowering – that is THE perfect time to cut it down. 

Cutting Blooming Thistle Plants

So, I find the plant in bloom (and hopefully it has not yet finished bloom and has moved on to setting seed) and then I use a pair of large sharp gardening loppers like these ones (the shears with long handles) to cut it down as close to ground level as I possibly can.

Now, the plant is at a real disadvantage! It’s completely in shock, because the only thing left is pretty much the root. It’s always beneficial to get rid of as many leaves left at ground level as possible. No leaves, no flowers, nothing but a root = a shocked plant.

Now, it has to find extra energy to completely rebuild itself. And it can do that, but it usually takes time. And once it does begin rebuilding itself, you cut it again.

Usually by the time you have cut it twice, it will die as it just cannot keep having to rebuild itself. The odd time you may need to cut a third time but usually it only takes two cuttings before the roots give up and die off.

Removing Thistle Plants that have gone to Seed

Never ever let a Canadian Thistle go to seed on your property if you can at all help it! One plant carries thousands of seeds and each will be able to start a new plant.

If one is too far gone and the seed heads are ready to let go, cover the plant with a large heavy duty garbage bag, then cut it down at the base.

This way, the seeds will let go while they are in the bag. This is a really safe way to get rid of thistle that is past the flowering stage.

We tend to bag up all the thistle plants and bring them to the dump. We sometimes burn the plants, but only if they are still in the flower stage. Once they move into setting seed, we do not burn them – it is much safer to get rid of the plant completely. We don’t want any seeds flying away!

Weed control should be done regularly! If you don’t want to have to cut down each of the thistle plants, my other option is to use a homemade all natural spray.

You can completely get rid of the weeds just by being able to stay on top of the spraying schedule, using this Canada thistle control with vinegar and soap.

Thistle Killer Recipe – Homemade Organic

This recipe will work on both the Scotch thistle and the Canada thistles – actually, it will work on any type of weed you have, including it’s ability to kill Poison Ivy plants. A great alternative to herbicides and other harsh chemicals you might find in 2,4-D, Roundup, and other herbicide treatments. This organic recipe works great on the persistence of these thistles.

You may need to repeat the spraying. You probably will. It’s organic right? So no chemicals can mean less toxicity.

Tips: If possible, use this spray during the hottest part of the day, when the plants are thirsty – the spray will be more beneficial.

Spray when there is no chance of rain in the forecast.

All Natural Weed Killer Ingredients

• 3 cups white vinegar
• 1/2 cup table salt
• 1 tablespoon liquid detergent or soap (I use Dawn) for stick-to-itiveness.

Directions to Mix Homemade Weed Killer

1. Mix vinegar and salt until the salt is completely dissolved. Stir in liquid dish soap, and pour into a spray bottle.
2. Spray onto the green growing leaves of the plants.
3. Wait a week, then repeat on any plants that are still alive. Best time to apply: during a dry spell.

For use on larger areas, simply triple or quadruple the recipe to give the quantity you need. Then, put the liquid into a backpack sprayer like this one. Make sure to get the stems and all other areas of the plant.

Canada Thistle Rash

Some people seem to be more sensitive than others to working with, and touching Canada Thistle and Scotch Thistle plants. Wearing long sleeves and long pants, plus wearing heavy leather gloves will go a long way towards being able to work with thistles. Try to be cautious of the flower-bud stage and not let the flower or plant touch your skin directly.

These tips will help if you do end up being in direct contact with the plant – Soothing Poison Ivy Rash 

Use this Canada Thistle Weed Killer on a regular basis throughout the growing season and you will see a huge difference in one year.

It’s one of the best and most natural ways to practice Canada Thistle control.

Originally published May 2022; latest update February 2026