The Dreaded Canada Thistle: What is it and How do I best treat it?


Is it just us, or do Canadian thistles have an uncanny power to take over yards no matter how hard you try to get rid of them? Canadian thistle (also known as creeping thistle, Canada thistle, Cursed thistle, or Cirsium arvense if you want to be fancy) can be a real headache. These invasive plants can take over your yard in no time! Keep reading to find out what these weeds are and how to manage them effectively.

What IS the Canadian Thistle?

If you live in Granby, you’ve probably seen the Canadian thistle around. This spiky plant with lavender to purple flowers spreads quickly through its root system, making it tough to get rid of. A mature Canada thistle plant is 2 to 5 feet tall, branching at the top. The leaves are 4 to 8 inches long, usually dark green with spiny serrated edges. Also called creeping thistle, this weed is a perennial invader that disrupts our gardens and lawns year after year. 

We’re plant experts at Country Ace and usually want to help you grow your lawn and garden. But the Canadian thistle is an invasive species, so we’re more than happy to talk about how to get rid of it! 

Why is the Canadian Thistle Bad?

The Canadian Thistle is more than just a nuisance – it spreads its roots far and wide, making it nearly impossible to eradicate. This perennial weed doesn’t just spoil the look of our yards; it also causes bigger problems for Grand County. Its aggressive nature allows it to take over, pushing out native plants and disrupting local ecosystems. Plus, pollinators might start favoring these invaders over native plants, which only makes things worse.

field of canadian thistles

Canadian Thistle in Granby

In Granby, the Canada thistle is classified as a noxious weed, meaning it is on the mandatory control list. Its prevalence is a concern for both homeowners and the community at large. Effective management and control are crucial to maintaining the beauty and health of our local environment.

Effective Treatment Strategies for Canadian Thistles

So, what can homeowners do about treating Canadian thistles? From weeding to pesticides, here are the best strategies for getting rid of those pesky weeds. 

We interviewed Keven Shanks from Scotts. Not only is he an expert on all things Scotts, but he’s been dealing with Canadian thistles for years! Keep reading for his professional tips and tricks for getting rid of Canadian thistles.

hand holding steel weed cutter

Weeding & Digging

One way to tackle Canadian thistle is through persistent weeding and digging. It’s a bit of a workout, but it can be effective if you stick with it. Make sure to dispose of the plants properly so they don’t reseed in your yard – remember, even tiny root fragments can regrow. At Country Ace Hardware, we’ve got all the gloves, shovels, and weeding tools you’ll need.

round up

Herbicides & Weed Killer 

Herbicides can be a powerful ally against thistles. Products like Roundup Weed Killer are great for this; you can find them at Country Ace Hardware. For the best results, apply herbicides when the thistles are actively growing, usually in spring to early summer or fall (keep reading for more details on timing!).

Persistence & Diligence 

The key to beating Canadian thistle is persistence. Keep up with your weeding and herbicide treatments, make sure you deal with the plants before they go to seed, and always dispose of them properly. Regular maintenance is crucial to keeping your yard thistle-free.

When To Start Treating Your Yard for Thistles in Granby 

Timing is everything when it comes to treating thistles. “The best time to treat Canada thistle is when it’s actively growing,” says Keven from Scotts. “To be more specific, the ideal time is early June, after the first flower buds are formed and before the first flowers open.  Another ideal time to treat is fall regrowth during September and early October.”

If you’re starting to notice those first flower buds, it’s time to treat them with Roundup Weed Killer!  Come to Country Ace today to get your weed control.

canadian thistle up close - purple flowers in field of grass

Handheld Pump

handheld pump

Backpack Sprayer

backpack sprayer

How to Treat Thistles with Native Grass

In Granby, many of us have native grasses, like buffalograss, in our yards. That means that controlling Canadian thistle requires a slightly tailored approach. Buffalograss, native to Colorado and much of the Great Plains, can be safely treated with several products. 

Keven, our Scotts representative, recommends products like Roundup For Lawns. As Keven points out, “In most cases, buffalograss is going to be the only native grass you will find on selective lawn weed control products sold at retail.” 

Products safe to use on Buffalograss:

When in doubt, check the label! While there are many products that won’t harm buffalograss, they might be an issue with other native grasses. 

If you have native grasses other than buffalograss, be cautious. Keven advises that while some selective lawn weed control products might be safe for other native grasses, they aren’t listed on the label. “We can’t recommend the product(s) for those grasses. In such cases, it’s best to consult a licensed professional applicator who has access to specialized pesticides for native grasses.”

When it comes to applying these treatments, consider the size of your area. For small areas, a handheld pump or hose-end sprayer will work well. For larger spaces, a backpack sprayer is more efficient. This approach ensures that you effectively manage Canadian thistles without harming your native grasses, making your property healthier and more beautiful.

What Product is Best for Me?

Not all yards are created equal! When we talked to Keven about the best Scotts products for treating the Canadian thistle, he told us that it depends on the yard and how big the problem is.

Here are some things to consider: 

  • How big is the problem?  Does the lawn contain a lot of Canada Thistle plants or just a few?
  • Have you fertilized the lawn recently?
  • Do you prefer to use a granular or liquid solution?

“For those who have lawns that contain a lot of Canada Thistle, a granular or concentrate liquid weed control is the best option,” according to Keven. 

scotts turf builder

Haven’t fertilized your lawn in a while? Use Scotts Turf Builder.

“If they haven’t fertilized the lawn in the last 6 to 8 weeks, they could use Scotts Turf Builder Weed & Feed or Scotts Step 2 Weed Control Plus Lawn Food.  If they choose to use a granular weed and feed product, be sure to apply the product to the lawn when the grass is wet. Early morning when there is dew on the lawn will work.”

“These products need to be applied when the grass is wet so the particles stick to the leaves or foliage of the Canada Thistle.  A lot of the active ingredients found in both granular and liquid weed control products will only enter the weed through the leaves or foliage.”

Fertilized your lawn recently? Try ready-to-spray products.

“If the consumer’s lawn contains a lot of Canada Thistle and they’ve fertilized recently or don’t want to fertilize, then use a ready-to-spray concentrate or concentrate product to treat a large area.

There are a few different products that can be used:

green bottle of weed killer

Just a few Canada thistles in your yard? Try spot treating with ready-to-use RoundUp

If you just have a few Canada Thistle plants in your lawn, spot-treating them with ready-to-use RoundUp for lawns is a great solution.

Check out these products:

It’s important to plan ahead if you’re taking this route because you’ll want to avoid everything getting wet for 24 hours after you apply. So, check the weather and turn off your sprinklers!

Get Your Lawn on a Program: Try Scotts 3 Step!

There’s more to weed control than just controlling the weeds. If you want to set yourself up for long-term success, consider implementing a program for lawn care and weed control.

“One of the best things a consumer can do to help prevent and/or reduce weed pressure in their lawn is to get on a program.” In Granby Colorado, we recommend Scotts 3 Step since we have such a short season.

“Feeding the lawn regularly throughout the growing season will help to thicken the turf, making it more difficult for weeds to compete and take over the lawn,” says Keven. 

Check out Scotts 3 Step Program at Country Ace! 

scots 3 step

Take on The Canadian Thistle with Country Ace

If you need a little encouragement, Keven has been in your shoes: “I’ve battled Canada thistle in my lawn in the past, and I can tell you that although it’s difficult to control, it can be done.  Canada thistle has an extensive root system and it will require multiple applications to successfully knock it out.  

I’ve had the greatest success spot treating the individual plants using the liquid weed control products listed above and making repeat applications at the recommended intervals found on the product label.” 

Dealing with Canadian thistle can be a daunting task, but with the right approach, it’s manageable. From persistent weeding and digging to using effective herbicides, there are several strategies to keep your lawn looking its best!

At Country Ace Hardware, we have everything you need, from quality tools and gloves to trusted products like Scotts weed killer. Visit us today, and we can work together to make your yard beautiful and thistle-free!

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