Question for gardeners - What is the best herbicide to get rid of Canada Thistle? An update

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worthit
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Question for gardeners - What is the best herbicide to get rid of Canada Thistle? An update

Post by worthit »

Hello:

What is the best herbicide to get rid of Canada Thistle? I would prefer something off the shelf that makes this less labor intensive.

Also, any suggestions on a good asset of thorn proof gloves for men and women as we are planning to pull these creatures out of the soil? They keep appearing every year and is a nuisance.

TIA.
Last edited by worthit on Sun Aug 02, 2020 6:53 am, edited 1 time in total.
Sconie
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Sconie »

Round Up will do it, but Canadian Thistle has quite a root system and will keep coming back unless you stay on top of the problem over the course of a couple of years.
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Re: Question for gardeners - What is the best heburbicide to get rid of Canada Thistle?

Post by livesoft »

Glyphosate will be the best herbicide. It will kill all plants that have not been genetically modified. There are many brands of weed killer that are made of glyphosate with Round-up being the most well known.

I guess for thistle that I would weed-whack them before they went to seed to about 6 inches high, then spray what's left with glyphosate when there will be no rain for a few days. Pull off any flower heads, too.

I don't know if this will work for thistle, but the Ortho nutsedge/kyllinga herbicide kills nutsedge and kyllinga which also have roots and nodules that regrow if the plant above the ground is pulled up. This herbicide won't kill other things, so check its label.
Last edited by livesoft on Sun Jul 26, 2020 9:28 am, edited 2 times in total.
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zlandar
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by zlandar »

Round Up (glyphosphate) will kill almost any plant in 2 weeks. Round Up is conveniently packaged pre-mixed or in concentrate while generic glyphosphate is usually concentrate only and I have to order online. The generic is way cheaper but you have to buy your own plastic sprayer and add a little surfactant. You can start with Round Up and if you find yourself spraying more than you thought you would move to the generic to save money.

Edit: fixed
Last edited by zlandar on Sun Jul 26, 2020 9:33 am, edited 1 time in total.
livesoft
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by livesoft »

zlandar wrote: Sun Jul 26, 2020 9:27 am Round Up (glycophosphate [glyphosate]) ...
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Havingfun1950
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Havingfun1950 »

Do not know “the best” but I have been satisfied with carefully aimed, spot application of Roundup. If the thistle is very close to a valued plant, I dig it up including as much root as possible. Either way, I treat twice a week and think that this frequency is important so that I get them while they are small and leave no stragglers to reproduce. When I dig, I wear heavy leather gloves. Good luck, they are noxious plants. And yes, I avoid contact with Roundup or other herbicides and read the application guidance.
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worthit
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

Thanks all. I was hoping to avoid using glyphosate due to all the recent evidence/controversy of them being carcinogenic. But seems like that is the only reasonable option.

Also, I came across these 2 models for gloves on Walmart's website - these are for women but they (G&F) make similar gloves for men too.

G & F Florist Pro Rose Gardening Gloves ~$13

G & F 2430M Florist Pro Long Sleeve Rose gardening Gloves, Thorn Resistant Garden Gloves, Rose Pruning Gloves ~ $18

Not sure what the difference would be but leaning towards purchasing the cheaper one.

Welcome if folks have opinions on these or would suggest some other brand for the gloves.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by WhyNotUs »

I use a high acid vinegar and manual removal once the number is manageable.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Mr. Rumples »

If it has an extensive root system as described in the link below, you need something to get in deep and it need to be applied at the right time of year. I was thinking of a poison ivy / brush killer; the link below recommends Speedzone, Tri-Mec, or Mecamine-D. When sprayed, they don't look like they are doing much of anything; it takes time to get to and kill the roots. To avoid spraying on other plants if you spot/target spray, take an old black plastic container, the type you get with plants from the store. I cut out the bottom and then nail an old 1"x2" x 3' board to it. You can put it around the target plant and avoid the rest.

https://www.tcweed.org/weed-of-the-mont ... a-thistle/
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by sport »

2,4-D is good for killing broad leaf weeds.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

WhyNotUs wrote: Sun Jul 26, 2020 9:48 am I use a high acid vinegar and manual removal once the number is manageable.
Thanks. I tried but looking to see if there are more effective, safe and lazy alternatives :D which I know doesn't exist when it comes to getting rid of these beasts.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by JS-Elcano »

I am avoiding all pesticides in my front and backyard. I pull all weeds with my hands and sometimes, like with thistles with longer roots, I'll dig it out. One has to stay on top of it (I spend some time every week to pull weeds). In over 12 years I have never used a pesticide. Great thing is also that I can use the grass clippings from weekly mowing as mulch for my garden beds and trees. So, depends how big the area is that you want to rid of thisle, but bying the herbicide, settig it all up and then going around and spot-treating everything, it is not only cheaper and healthier to pull/dig the weeds but might also be faster :sharebeer
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

Mr. Rumples wrote: Sun Jul 26, 2020 9:51 am If it has an extensive root system as described in the link below, you need something to get in deep and it need to be applied at the right time of year. I was thinking of a poison ivy / brush killer; the link below recommends Speedzone, Tri-Mec, or Mecamine-D. When sprayed, they don't look like they are doing much of anything; it takes time to get to and kill the roots. To avoid spraying on other plants if you spot/target spray, take an old black plastic container, the type you get with plants from the store. I cut out the bottom and then nail an old 1"x2" x 3' board to it. You can put it around the target plant and avoid the rest.

https://www.tcweed.org/weed-of-the-mont ... a-thistle/
Than Mr. Rumples. Currently these are confined only to the flower beds (not the lawn) in front of the house and they look like the spring flush in the link you provided.
sport wrote: Sun Jul 26, 2020 9:58 am 2,4-D is good for killing broad leaf weeds.
https://homeguides.sfgate.com/use-24d-h ... 24530.html
Thank you, sport. I will look into these as well.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by BogleTaxPro »

worthit wrote: Sun Jul 26, 2020 9:43 am Also, I came across these 2 models for gloves on Walmart's website - these are for women but they (G&F) make similar gloves for men too.

G & F Florist Pro Rose Gardening Gloves ~$13

G & F 2430M Florist Pro Long Sleeve Rose gardening Gloves, Thorn Resistant Garden Gloves, Rose Pruning Gloves ~ $18

Not sure what the difference would be but leaning towards purchasing the cheaper one.

Welcome if folks have opinions on these or would suggest some other brand for the gloves.
We don't have Canada thistle but we have bougainvillea, which has thorns like nails (especially when it's overgrown). I've tried a few of these types of gloves and they mostly help with scratches...which can be pretty nasty by themselves...but if you grab a thorn straight on, it's still going to possibly puncture the glove. I do suggest wearing these, but do still be careful.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

JS-Elcano wrote: Sun Jul 26, 2020 10:02 am I am avoiding all pesticides in my front and backyard. I pull all weeds with my hands and sometimes, like with thistles with longer roots, I'll dig it out. One has to stay on top of it (I spend some time every week to pull weeds). In over 12 years I have never used a pesticide. Great thing is also that I can use the grass clippings from weekly mowing as mulch for my garden beds and trees. So, depends how big the area is that you want to rid of thisle, but bying the herbicide, settig it all up and then going around and spot-treating everything, it is not only cheaper and healthier to pull/dig the weeds but might also be faster :sharebeer
Thanks JS-Elacano.

I have an aversion (and sensitivity) to chemicals generally. So I also have been digging them out for the past 5 years except for trying vinegar/soap mixture over a small area last year (with some success). In fact, it isn't a large area. I think it would be best to do the manual work as you indicate for both health and being the cheapest option. I was just getting lazy and only wanted an easy way out :oops:.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Mr. Rumples »

JS-Elcano wrote: Sun Jul 26, 2020 10:02 am I am avoiding all pesticides in my front and backyard. I pull all weeds with my hands and sometimes, like with thistles with longer roots, I'll dig it out. One has to stay on top of it (I spend some time every week to pull weeds). In over 12 years I have never used a pesticide. Great thing is also that I can use the grass clippings from weekly mowing as mulch for my garden beds and trees. So, depends how big the area is that you want to rid of thisle, but bying the herbicide, settig it all up and then going around and spot-treating everything, it is not only cheaper and healthier to pull/dig the weeds but might also be faster :sharebeer
I would agree...I only spray for poison ivy, but since the poster asked I answered. Since it is only a few plants in a limited area, it might be manageable by killing them and depriving the root system of food.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

BogleTaxPro wrote: Sun Jul 26, 2020 10:03 am
worthit wrote: Sun Jul 26, 2020 9:43 am Also, I came across these 2 models for gloves on Walmart's website - these are for women but they (G&F) make similar gloves for men too.

G & F Florist Pro Rose Gardening Gloves ~$13

G & F 2430M Florist Pro Long Sleeve Rose gardening Gloves, Thorn Resistant Garden Gloves, Rose Pruning Gloves ~ $18

Not sure what the difference would be but leaning towards purchasing the cheaper one.

Welcome if folks have opinions on these or would suggest some other brand for the gloves.
We don't have Canada thistle but we have bougainvillea, which has thorns like nails (especially when it's overgrown). I've tried a few of these types of gloves and they mostly help with scratches...which can be pretty nasty by themselves...but if you grab a thorn straight on, it's still going to possibly puncture the glove. I do suggest wearing these, but do still be careful.
Thanks, BogleTaxPro.

Agree, bougainvillea thorns are even worse in my book relative to the thorns on these beasts at least when they are just growing out.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by livesoft »

Mr. Rumples wrote: Sun Jul 26, 2020 9:51 am... To avoid spraying on other plants if you spot/target spray, take an old black plastic container, the type you get with plants from the store. I cut out the bottom and ...
I do something similar with plastic 2 liter soda Dr Pepper bottles. I found this idea somewhere on the internet:

Usually I cut off 3 to 4 inches of the bottom of the bottle, thread the offending weed or vine through the screw-cap opening and push that down to the ground. Spray the weed held inside the bottle with herbicide and then place the bottom on top. Here's a picture:
Image

I don't think one can use this with thistle necessarily unless one cuts off the threads of the bottle cap to make a large opening to put over the plant. Note that breaking off leaves as one shoves the bottle over the plant is not a problem because one wants the plant dead anyways. The funnel-down aspect of the bottle also directs overspray of the herbicide to the localized area around the stem and roots there. The bottle prevents impending rain from washing off the herbicide, too, and perhaps overheats the plant on sunny days. In other words, this "Dr Pepper bottle system" has a lot going for it including the ability to use the Dr Pepper beforehand when making oatmeal.

Added: I just now thought of a modification: Cut the bottle cylinder lengthwise which would allow it to be spread open and let one "wrap" it around any stalk without having to thread the plant through the narrow opening.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by vineviz »

worthit wrote: Sun Jul 26, 2020 10:11 am
JS-Elcano wrote: Sun Jul 26, 2020 10:02 am I am avoiding all pesticides in my front and backyard. I pull all weeds with my hands and sometimes, like with thistles with longer roots, I'll dig it out. One has to stay on top of it (I spend some time every week to pull weeds). In over 12 years I have never used a pesticide. Great thing is also that I can use the grass clippings from weekly mowing as mulch for my garden beds and trees. So, depends how big the area is that you want to rid of thisle, but bying the herbicide, settig it all up and then going around and spot-treating everything, it is not only cheaper and healthier to pull/dig the weeds but might also be faster :sharebeer
Thanks JS-Elacano.

I have an aversion (and sensitivity) to chemicals generally. So I also have been digging them out for the past 5 years except for trying vinegar/soap mixture over a small area last year (with some success). In fact, it isn't a large area. I think it would be best to do the manual work as you indicate for both health and being the cheapest option. I was just getting lazy and only wanted an easy way out :oops:.
For spot treatment, I use a small bottle/brush combo like you’d find in an art supply store for applying rubber cement. With a screw on lid.

Put glyphosate concentrate in the bottle, then paint it on the cut stem of the thistle or other plant. This avoids spraying, therefore less worry about aerosolizing the herbicide: much less inhalation risk and much less drift into nearby desirable plants.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Mudpuppy »

BogleTaxPro wrote: Sun Jul 26, 2020 10:03 am
worthit wrote: Sun Jul 26, 2020 9:43 am Also, I came across these 2 models for gloves on Walmart's website - these are for women but they (G&F) make similar gloves for men too.

G & F Florist Pro Rose Gardening Gloves ~$13

G & F 2430M Florist Pro Long Sleeve Rose gardening Gloves, Thorn Resistant Garden Gloves, Rose Pruning Gloves ~ $18

Not sure what the difference would be but leaning towards purchasing the cheaper one.

Welcome if folks have opinions on these or would suggest some other brand for the gloves.
We don't have Canada thistle but we have bougainvillea, which has thorns like nails (especially when it's overgrown). I've tried a few of these types of gloves and they mostly help with scratches...which can be pretty nasty by themselves...but if you grab a thorn straight on, it's still going to possibly puncture the glove. I do suggest wearing these, but do still be careful.
That's my experience as well. I wear thick gardening gloves with leather reinforced palm and fingers, and a breathable fabric back side. They work well for almost all of my thorny plants except two. Both of those plants have long, thick thorns and they'll poke right through the glove if I grab a thorn straight on. I have thick leather gloves as well, but I can get poked by those two plants through even the leather gloves, so I stick with the more breathable gardening gloves most days.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Northern Flicker »

Your local county extension master gardener's chapter may have a support infrastructure you can engage to get ideas less heavy handed than round-up, which works well unless you have other things you want to grow in the space or are concerned about toxicity or carcinogenesis. Use of pesticides and herbicides also may kill or chase away bugs, beneficial soil bacteria, etc, things that are part of a healthy soil ecosystem.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by AK1236 »

Stinger...follow the label.
no longer in the weeds and thorns
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Re: Question for gardeners - What is the best heburbicide to get rid of Canada Thistle?

Post by Sandtrap »

livesoft wrote: Sun Jul 26, 2020 9:17 am Glyphosate will be the best herbicide. It will kill all plants that have not been genetically modified. There are many brands of weed killer that are made of glyphosate with Round-up being the most well known.

I guess for thistle that I would weed-whack them before they went to seed to about 6 inches high, then spray what's left with glyphosate when there will be no rain for a few days. Pull off any flower heads, too.

I don't know if this will work for thistle, but the Ortho nutsedge/kyllinga herbicide kills nutsedge and kyllinga which also have roots and nodules that regrow if the plant above the ground is pulled up. This herbicide won't kill other things, so check its label.
We have 20 acres of Russian Thistle that we keep mowed down to 6" before it gets "wooded".
I saturate the fence lines clear with generic Glycosyphate. (25 gallon tank on the back of an ATV)
Russian Thistle, like many Russian things, is tough tough tough, but this works. It takes time and is not instant but does knock the stuff down.

It is best to spray when there are leaves on the plant so it can be absorbed.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Flobes »

worthit wrote: Sun Jul 26, 2020 9:05 am What is the best herbicide to get rid of Canada Thistle?
...
I was hoping to avoid using glyphosate due to all the recent evidence/controversy of them being carcinogenic. But seems like that is the only reasonable option.
My war on thistles has been won using Avenger.

When I moved here, it was a thistle jungle. Canada (and other) thistles are officially designated as "noxious weeds" in my state, and it's my civic duty to stop their spread.

I do not follow the Avenger instructions. Rather, I apply it with an artists brush, painting directly onto thistle leaves, undiluted. That way, it does not kill other plants around it, as spraying would. Leaves turn black in a few hours, and the plant dies within a day.

It took several years to get them darn thistles under control. Now I have just a few each year, perhaps brought by the winds and the birds, and those uninvited thistles are treated to Avenger breakfast on a bright sunny morning.

Product: Avenger Weed Killer Concentrate, For Organic Gardening. It's a citrus-based product, biodegradable, non-toxic: safe for garden, safe for pets, safe for you. An organic farmer turned me on to it. Amazon, of course, stocks it.
worthit wrote: Sun Jul 26, 2020 9:05 am ...we are planning to pull these creatures out of the soil
Every year, we attacked the thistles: pulled and trimmed and dug and and pulled some more. I eventually contacted the Extension Service, and their weed guy came for a site visit. He advised to stop digging and pulling; it actually strengthens the extensive underground root system. To eradicate, thistles must be poisoned, and then pulled only once they are completely dead.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

Thank you, all.

Very informative. I am going to look into each one of your valuable suggestions.

By the way, just wanted to share something interesting.

While researching this, I came across a glove on reddit that the user claims is the best he has ever used after trying a number of the typical ones available on Amazon and with other sellers including all the expensive ones. The best part is, it is only $3, but available only in a Canadian chain called Dollarama. It is called Duramax pro, latex coated work gloves. He has the picture too. As far as I can tell, Walmart has similar work gloves but listed for ~ $15. I am going to look into them even though I have already ordered the G&F ones on Amazon. Thinking of double gloving if it is possible.

He has a review post and the picture if anyone is interested in checking it out - simply google best gloves for Canada thistle reddit review.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by InMyDreams »

"Goats are hired to eat the following weeds:

Canada Thistle"

https://goatseatweeds.com/frequently-asked-questions/
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Voltaire2.0 »

I use Natria as an broad spectrum alternative to Round-Up.

It does nor work at predictably as Round-Up in that it kills some plants within minutes (not exaggerating) but others are immune. I use it on blackberry.

You need to test it on your targets, and it does not contain glyphosate.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Mudpuppy »

worthit wrote: Mon Jul 27, 2020 7:10 am While researching this, I came across a glove on reddit that the user claims is the best he has ever used after trying a number of the typical ones available on Amazon and with other sellers including all the expensive ones. The best part is, it is only $3, but available only in a Canadian chain called Dollarama. It is called Duramax pro, latex coated work gloves. He has the picture too. As far as I can tell, Walmart has similar work gloves but listed for ~ $15. I am going to look into them even though I have already ordered the G&F ones on Amazon. Thinking of double gloving if it is possible.

He has a review post and the picture if anyone is interested in checking it out - simply google best gloves for Canada thistle reddit review.
I've not had good luck with nitrile coated gloves resisting thorns, which is in the same family of gloves as the ones you're discussing. It really depends on how thick the underlying knit layer is and on how thick the coating layer is. But the issue I've had with this type of gloves is once a thorn or a splinter from bark mulch/ compost works its way into the knit layer on the back side of the hand, the gloves are no longer comfortable.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by Mudpuppy »

And while I don't have Canada thistle here in California, I do have a lot of neighbors with invasive trees and therefore a lot of unwanted tree seedlings popping up against the fence line. The gardener for the previous owner just cut the seedlings back level with the shrubbery, so when I moved in, there was a lot of cleanup needed.

I found that a brush and vine herbicide containing triclopyr or it's derivatives brushed directly on the freshly cut stump does the trick to kill the roots and keep them from coming back, without killing the surrounding shrubs. I've used it on a wide variety of unwanted tree seedlings, virginia creeper, and even palm trees.

Looking at the safety directions for my current bottle, there is risk of eye damage with triclopyr, so I wouldn't recommend spraying it, but it works well when brushed on. This is one of the cases where I wear the nitrile coated gloves to apply the herbicide, then immediately take the gloves off and wash up so I don't accidentally rub my eyes when my hands have residue of the herbicide.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

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I have a pair of thick fire resistant leather gloves - the kind where you can reach into a campfire and move around burning logs - that work great for protecting against heavy thorns. Not the best to work in, but I use them when pruning rose bushes.
Last edited by Kenkat on Mon Jul 27, 2020 1:44 pm, edited 1 time in total.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by wfrobinette »

worthit wrote: Sun Jul 26, 2020 9:05 am Hello:

What is the best herbicide to get rid of Canada Thistle? I would prefer something off the shelf that makes this less labor intensive.

Also, any suggestions on a good asset of thorn proof gloves for men and women as we are planning to pull these creatures out of the soil? They keep appearing every year and is a nuisance.

TIA.
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by iamlucky13 »

worthit wrote: Sun Jul 26, 2020 9:59 am
WhyNotUs wrote: Sun Jul 26, 2020 9:48 am I use a high acid vinegar and manual removal once the number is manageable.
Thanks. I tried but looking to see if there are more effective, safe and lazy alternatives :D which I know doesn't exist when it comes to getting rid of these beasts.
Horticultural vinegar is fairly caustic. Citric acid is probably similar. You need to be careful handling it. Household vinegar might be strong enough, but it probably depends on the plant. I also read several of the studies on glyphosate that were spun by the media and others as controversial. The actual details in those studies made me very comfortable continuing to use glyphosate.

Any of these will kill the top. The root will likely grow new shoots several times, but regular treatment will eventually deplete the nutrients stored in the roots.

In my yard, the Canada thistle eventually died off once I caught up with regular mowing (neglected by the previous owner). Shorter growing thistles are more resilient to mowing. In a few areas close to the house, I dealt with the thistles more quickly by pulling.

Decent leather gloves help, but I can pull them reasonably comfortably in cotton gloves by reaching to the very base where the thorns are fewer and softer, and moving my fingers slightly upward as I grip it in order to fold the thorns upward against the stem. Depending how hard the soil is, sometimes I use a dandelion tool to loosen the soil around the taproot before pulling.
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Re: Question for gardeners - What is the best heburbicide to get rid of Canada Thistle?

Post by Ged »

livesoft wrote: Sun Jul 26, 2020 9:17 am
I guess for thistle that I would weed-whack them before they went to seed to about 6 inches high, then spray what's left with glyphosate when there will be no rain for a few days. Pull off any flower heads, too.
I would not cut the plants down before spraying with glyphosate. The herbicide is normally adsorbed through the leaves. By removing all leaves there is no way for the herbicide to get into the plant.
livesoft
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Re: Question for gardeners - What is the best heburbicide to get rid of Canada Thistle?

Post by livesoft »

Ged wrote: Mon Jul 27, 2020 2:30 pmI would not cut the plants down before spraying with glyphosate. The herbicide is normally adsorbed through the leaves. By removing all leaves there is no way for the herbicide to get into the plant.
Yes, that is true, but my personal experience shows that glyphosate is taken up by roots as well. And since this plant seems to re-sprout from roots, getting some glyphosate into the soil that the roots are in would not be a bad thing.

But the OP can do this experiment:
1. Leave some thistle untreated as as control.
2. Treat some thistle without weed-whacking.
3. Weed-whack and treat the weed-whacked thistle.

Be sure to have all the plants far enough apart so that they don't affect each other, but close enough together so that they get the sun and water.

What are the results?

The OP can also use other treatments during the same experiment to see what works better and what doesn't work so well.
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suemarkp
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by suemarkp »

Crossbow is one I like for woody plants (and weeds too). It does not kill grass or many plants, so that makes it easier to spray indiscriminately. I use it most for blackberry control. Ingredients are: 2,4-dichlorophenoxyacetic acid, butoxyethyl ester, triclopyr BEE: 3,5,6-trichloro-2-pyridinyloxyacetic acid, butoxyethyl ester.

The Crossbow label says it deals with Canada Thistle, but you need to use it at the highest concentration and it only does top growth control. So maybe it isn't the best choice for this thistle. But if you hit it a couple of times a year and can keep it cut (e.g. lawnmower), it will probably die off.

https://www.domyown.com/msds/Crossbow_Label2w.pdf
Mark | Kent, WA
livesoft
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by livesoft »

suemarkp wrote: Mon Jul 27, 2020 4:24 pm ... Ingredients are: 2,4-dichlorophenoxyacetic acid, butoxyethyl ester,
This is the long name for 2,4-D.
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worthit
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Re: Question for gardeners - What is the best herbicide to get rid of Canada Thistle?

Post by worthit »

Flobes wrote: Sun Jul 26, 2020 11:41 pm
worthit wrote: Sun Jul 26, 2020 9:05 am What is the best herbicide to get rid of Canada Thistle?
...
I was hoping to avoid using glyphosate due to all the recent evidence/controversy of them being carcinogenic. But seems like that is the only reasonable option.
My war on thistles has been won using Avenger.

When I moved here, it was a thistle jungle. Canada (and other) thistles are officially designated as "noxious weeds" in my state, and it's my civic duty to stop their spread.

I do not follow the Avenger instructions. Rather, I apply it with an artists brush, painting directly onto thistle leaves, undiluted. That way, it does not kill other plants around it, as spraying would. Leaves turn black in a few hours, and the plant dies within a day.

It took several years to get them darn thistles under control. Now I have just a few each year, perhaps brought by the winds and the birds, and those uninvited thistles are treated to Avenger breakfast on a bright sunny morning.

Product: Avenger Weed Killer Concentrate, For Organic Gardening. It's a citrus-based product, biodegradable, non-toxic: safe for garden, safe for pets, safe for you. An organic farmer turned me on to it. Amazon, of course, stocks it.
worthit wrote: Sun Jul 26, 2020 9:05 am ...we are planning to pull these creatures out of the soil
Every year, we attacked the thistles: pulled and trimmed and dug and and pulled some more. I eventually contacted the Extension Service, and their weed guy came for a site visit. He advised to stop digging and pulling; it actually strengthens the extensive underground root system. To eradicate, thistles must be poisoned, and then pulled only once they are completely dead.
Just wanted to thank everyone for their responses and provide an update.

Since I wanted a chemically less intense (non-carcinogenic) product that wouldn't introduce other headaches, I decided to go with Avenger (Thanks, Flobes) after researching the product. It appears to be non-toxic. I applied them to the leaves using a small paint brush as mentioned in Flobes post. The effect was impressive - the weeds darkened and died within 30 minutes to an hour after application. Next step is to pull them which by the way is my exercise for today :happy.
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Re: Question for gardeners - What is the best heburbicide to get rid of Canada Thistle?

Post by JBTX »

livesoft wrote: Mon Jul 27, 2020 2:39 pm
Ged wrote: Mon Jul 27, 2020 2:30 pmI would not cut the plants down before spraying with glyphosate. The herbicide is normally adsorbed through the leaves. By removing all leaves there is no way for the herbicide to get into the plant.
Yes, that is true, but my personal experience shows that glyphosate is taken up by roots as well. And since this plant seems to re-sprout from roots, getting some glyphosate into the soil that the roots are in would not be a bad thing.

But the OP can do this experiment:
1. Leave some thistle untreated as as control.
2. Treat some thistle without weed-whacking.
3. Weed-whack and treat the weed-whacked thistle.

Be sure to have all the plants far enough apart so that they don't affect each other, but close enough together so that they get the sun and water.

What are the results?

The OP can also use other treatments during the same experiment to see what works better and what doesn't work so well.
I'm not at all an expert, but my understanding was round up became essentially inert on soil, such that soaking into the ground to the roots is not how it works. It has to be absorbed by the body of the plant then travels down to the root.
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