How To Get Rid Of Canadian Thistle

Filed Under: Weeds, Weeds and Invasive Plants · Keywords: How To, Get Rid Of, Kill, Eliminate, Eradicate, Canadian, Thistle · 1754 Views
I have tried tirelessly to get rid of the overwhelming growth of Canadian Thistle to no avail. Please HELP

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Additional comments about this question: · Gardenality Genius · Zone 8A · 10° to 15° F
Hi Mary, Where is the Canadian Thistle growing? In the lawn, veggie garden, flower beds, or in plant beds and/or islands? I need to know this before giving you instruction on how to eradicate this problem weed. Also, have you used any weed control products? -Brooks Wilson

6 years ago ·
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Answer #3 · Max Taggart's Answer · Mary, I am in far Eastern Oregon, Zone 6A, with 15 acres in alfalfa and 1 acre in landscape and lawn. When I moved out here in agriculture area, I had four thistle types, including Canadian. It is a constant battle, but what I use as my "go to" broadleaf herbicide is Dicamba. It is nonrestricted, which means you can buy and apply without a license. It is similar, but far superior, to 24-D; it is sold under various trade names and you may have to go to a "farm chemical" store, like a co-op to find it but it is a common herbicide. Late Fall is the best time to get the best kill because most plant, including weeds, store carbs for the next year; uptake into the plant is better. Dicamba is one of two herbicides that is actually able to control, as opposed to suppress, bind weed, aka Morning Glory. Be patient, You can win! Max Taggart.)

Additional comments about this answer: · Gardenality Genius · Zone 8A · 10° to 15° F
Hi Max, I agree with you. In my answer both of the products I listed contain Dicamba. And yes, she can win!. Thank you for your good answer. - Brooks Wilson

6 years ago ·
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Answer #1 · Mary B's Answer · It is grows just about everywhere. It has caused me to give up on planting anything in the foundation areas of my house. I could weed day in and day out. I have sprayed, pulled, dug, sifted through the dirt to get any traces of the smallest roots. I have left the areas most effected untouched. I am hoping there is something I can do now before the weather turns to help eliminate the problem in the spring. Any advise is GREATLY appreciated.-Mary B)

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Answer #2 ·'s Answer · Hi Mary,

Repeated applications of herbicide/weed killer is the only real solution. The roots grow very wide and very deep so it will take several applications to get enough of the herbicide into the roots to kill the entire plant. The key principle to Canadian Thistle control is to stress the plant and force it to use stored root nutrients. If not treated regularly Canadian Thistle will recover and continue to grow. It is impossible to pull up the root system due to the fact that the roots go so wide and so deep. Successful eradication could take years of continued spraying depending on the maturity of the root system.

In non-lawn areas such as beds and islands Glyphosate can be used. Round-Up and Killz-All are perhaps the most popular varieties. Adding a surfactant/sticking agent is recommended. Fall is the best time to begin treatment with Glyphosate. Repeat applications next Spring and Fall will be necessary as well. Continue this spraying regimen until complete eradication has been achieved. Get ready for a battle. This could take a few or more years.

In lawn areas use a 2-4-D product such as Fertilome Weed-Out Lawn Weed Killer or Montery Weed Whacker. Both contain 2-4-D as well as other herbicides that will aid in the process of eliminating the Canadian Thistle and other broadleaf weeds. Again, repeated applications will be necessary using the same spraying schedule as the Glyphosate. Do not use granular products containing 2-4-D, such as weed and feed products or lawn weed killer granules, as they are generally less effective due to lack of herbicide contact with the foliage. Don't let anyone sell you pre-emergent weed control products. Canadian Thistle is a perennial weed and pre-emergents will not be effective.

As with all chemicals make sure to read the product labels carefully and follow the mixing and spraying instructions.

You can also try laying plastic over the Canadian Thistle, however, the roots can spread over 20 feet in width. This considered, it may be difficult to know how much plastic to lay and how wide an area to cover.

Hope this helps you!

Brooks Wilson:))

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