Canada Thistle Control

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Emulsifiable Concentrate (EC)
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Nanotek Surfactant
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Keith's Pro Tips

"Most herbicides suppress Canada thistle top growth only but because of the persistent root system, suppressing the top growth is like giving the thistle a haircut. The only effective long-term control strategy is a systemic herbicide that translocates deep into the roots like 2,4-D."

Canada Thistle Control: How to Get Rid of Canada Thistle

Canada Thistle is a common invasive plant found in a wide range of areas, especially in the upper mid-west of the United States like in Indiana and Wisconsin. Canada Thistle is a creeping perennial and often it is seen in growing in large patches where established. Its typically seen in a wide range of areas but it tends to thrive more where it is wet.

This broadleaf weed isn't just a problem on home lawns, it is also a huge issue to farmers and growers in the agricultural industry, especially in Canada as its name implies. Canada Thistle can cause greater crop losses than any other perennial broadleaf weed in various regions and it continues to spread. It's the number one perennial broadleaf weeds farmers target.

If you are having a problem with Canada Thistle, we can help. Our DIY Canada Thistle control guide was developed by our team of lawn care experts to show you exactly what you need to kill Canada thistle and eradicate it from your yard quickly and affordably.

Identification

Before you can carry out a treatment plan, you need to both be aware of what Canada Thistle looks like and to confirm whether or not it is the weed you are dealing with. Misidentification can lead to using the wrong treatment methods, which can end up wasting your time and money. Its important to differentiate Canada Thistle from many of the biennial thistles that can grow since the methods of treating them are quite different.

Canada Thistle

  • Canada thistle is a perennial weed that can grow up to 5 feet tall and branch out horizontally on the top portion of its slender, grooved, and erect stems. Each weed has fibrous taproot that is up to six feet deep. This extensive root system is what makes the Canada thistle especially difficult to control.
  • The leaves are lance-shaped and have prickly wavy margins that attach directly to the stem. Depending on the stage of growth and species, the leaves will vary from having no lobes to irregular deep lobes.
  • When maturing, Canada Thistle produces these small light fluffy seeds which can blow off and disperse, similar to dandelion. Much of the seed tends to just drop right where the parent plant is.
  • Between June to August, this weed will begin to display clusters of rounded, umbrella-shaped flowers at the tops of branches. These flowers vary in purple, pink, to pale pink in color. Canada Thistle flowers are also unique because they have both male and female flowers which are very small compared to other thistles. The gender of the flower will determine its fragrance, size, and shape. Male Canada thistles will be smaller, less fragrant, and more globe-shaped than female flowers.

Use the above description and image to help you in properly identifying Canada thistle. If you are having trouble, you can always contact us and our lawn care experts will help to correctly ID your weed growth and suggest treatment options.

Inspection

Once the Canada Thistle has been properly identified, you can then move on to inspection. During this phase of the program, you will need to locate where the Canada Thistle is growing and what the conditions of the area are that are allowing it to thrive. This will help you in determining where to focus your herbicide application.

Canada Thistle

Where to Inspect

Canada thistle grows well in disturbed soil with regular aeration that has full or partial access to sunlight. Common sites include but are not limited to pastures, fields, croplands, fallow land, forest openings, and roadsides.

What to Look For

Once established, Canada thistle will begin to form dense, and erect patches or clumps between June to August. During the early spring and fall, this weed will appear as a rosette.

Treatment

Before using any herbicide product, make sure you first have on the proper personal protective equipment (PPE) for safety when mixing and applying.

We recommend using a selective post-emergent herbicide containing one of the active ingredients like glyphosphate, triclopyr, or 2,4-D to kill Canada Thistle. A herbicide containing systemic activity will help to target the Canada Thistle down to its roots and leave desired plants unharmed. If your selected herbicide allows it, using a surfactant with your applications will result in better elimination.

If Canada Thistle is growing in warm-season lawns or in non-lawn areas, you may have to use a non-selective herbicide that contains an active ingredient like glyphosate. Non-selective herbicides kill any plant they are applied to, including grass.

No matter which herbicide is used, it will take consistent applications to fully control Canada thistle. These perennial weeds can create new infestations from plant cuttings, dislodged roots, or leftover root material beneath the soil. Be sure to follow all reapplication rates and restrictions on the product label. 

Step 1- Measure and Mix 2,4-D Amine

Mixing 2,4-D Amine

2,4-D Amine Selective Post-Emergent Herbicide is a selective herbicide that kills broadleaf weeds and brush without harming cool-seasoned grasses when used according to the label instructions. 

Nanotek Surfactant is a non-herbicide product that will help this product to stick better to the weed and make the herbicide work more effectively.

Determine how much 2,4-D Amine Selective Post-Emergent Herbicide to use by measuring the square footage of the treatment area. To do this, measure the length and width of the treatment area in feet then multiply them together (length X width = square footage). For acreage, take the square footage of the treatment area and divide it by one acre (square footage / 43,560 sq. ft. = acres).

When using 2,4-D Amine to control weeds in ornamental turf, the labeled application rate for this product is 3.16 pints of concentrate per 1 acre. For smaller applications, this breaks down to 1.1 fluid ounces of concentrate applied over 1,000 square feet.

In pastures and rangelands, mix 1 to 4 pints of concentrate in 1 to 30 gallons of water per acre. For smaller areas, you can mix ¾ to 1 fluid ounce of concentrate mixed into 1 gallon of water to apply over 1,000 square feet.

In fallow lands, mix 4 pints of concentrate into 10 gallons of water.

Simply add 1 fl. oz. of Nanotek Surfactant with every 1 gallon of 2,4-D Amine Selective Post-Emergent Herbicide.

Once you have made your measurements and calculated how much product you need, mix the product and surfactant with the appropriate amount of water in a handheld or backpack sprayer. Shake the sprayer to ensure the solution is well-mixed and then you're ready to spray.

Step 2 - Apply 2,4-D Amine To The Canada Thistle

Spray the invading Canada Thistle

Applications are most effective when the plant is budding before seed production. If the plants are close to producing seeds, you may need to mow the plant to prevent the weed from spreading.

The taproot will survive and grow a new plant over the next year, providing another opportunity to apply chemical control. Keep in mind that mechanical removal alone is not recommended, as it is easy to leave even a small part of the taproot in the ground when pulling weeds. As long as a portion of the taproot remains alive, weeds like Canada Thistle will continue to grow and take resources away from your other plants.

Adjust your sprayer a sprayer to a fan nozzle setting for even coating of 2,4-D Amine Selective Herbicide mixture on the top and bottom of Canada thistle leaves. Spray the weed to the point of wet, but just before the point of runoff.

Avoid applications when temperatures are above 90 degrees Fahrenheit. Because Canada thistle is so prolific, you may need to do repeated applications until you no longer see any more Canada Thistle.

Do not make more than 2 applications per year on ornamental turf, pastures, rangelands, and fallow lands.

Do not disturb treated fallow land areas for at least 2 weeks after treatment, or until weed tops are dead.

Prevention

Once Canada thistle has been removed from your property, be sure it does not make a return. Some preventative measures you can take to prevent Canada thistle are explained below:

Hand Pulling Weed

  • Limit ground disturbance from vehicles, machinery, and grazing livestock since Canada thistle grows well in sites with consistent aeration and well-drained soils. Best to rotate livestock between fields for each season to limit possible soil disturbances.
  • Take note of where current and previous infestations of this weed are present and make applications with 2,4-D Amine Selective Post-Emergent Herbicide as they occur. Keeping up with consistent post-emergent applications will work best to control this weed.
  • Check and map out areas in your property that have present Canada thistle. Either pull the weed out by hand or avoid mowing these areas all together until the weed is removed. Mowing over this foliage can spread the infestation further into your property. Clean your application tools and clothing before entering and exiting the treated area.

Key Takeaways

What is Canada Thistle?

  • Canada Thistle is an invasive creeping perennial that creates large patches where established and is a common threat to homes and agricultural lands in the upper mid-west.

How To Get Rid of Canada Thistle

  • We recommend 2 4-D Amine Herbicide to treat Canada thistle. It is selective and will kill the plant all the way down to the root.

Preventing Reestablishment of Canada Thistle

  • To prevent Canada Thistle, implement proper cultural practices such as watering, mowing and feeding to make your yard less conducive to Canada thistle making a return and invading your yard.

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