Most of the thistles are prolific seeders and birds like them and help spread them all over the place, so sometimes uprooting is not enough. The best method is to eliminate all of the thistle plants for miles around, but that is not always possible, and mulches seem to provide a very good germination bed for the seeds.

Different thistles prefer different growing conditions so it may depend on which one you have what might be done to the soil that could help keep them down.

kimmq is kimmsr

It would help help help you if you posted a picture of the troublesome thistle. Different kinds require different methods.

'thistles grown as flowers' ..... I suspect they didn't fully recognise what they were seeing. None of the weedy thistles are intentionally grown as garden flowers. They are as troublesome here as anywhere. They might have seen Onopordiums, Artichokes, Cardoons or Echinops but certainly not the weed species.

I was recently asked by a visitor from Bakersfield about some puzzling 'wild flowers' they had seen in a park. They were Crocuses.

I have a good friend who was born, grew up and lived his first 35 years in London. He's a master of friendly sarcasm. BUT, his facial gestures let me know it's sarcasm. I guess my own friendly sarcasm without the accompanying face-to-face signals fell flat. Sorry.

I didn't REALLY think the solution to her problem was to paint a pretty sign and let thistles grow. I was more commenting on my brother and SIL's lack of plant knowledge and their "discovering a new plant species for their flower beds".

I suggested what I would do to try to actually get rid of them in the second paragraph.

No need to explain - the suggestion for a sign was clearly humorous. That wasn't my point. I was just suggesting what the 'thistles' your brother saw might have been have been.

Ask your friend if he'd do the facial sarcasm signals if he was back in London. An interesting discussion might ensue.

You may have Canada Thistle. Search it on the internet to see pictures and how noxious of a weed it is. It makes a very large root that goes horizontal very deep inthe soil and cant be dug up once established. Depending on how long it has been there, you may need an herbicide like round-up to eliminate it. Dont ignore canada thistle.

Yes it is definitely Canada Thistle! Why me! :) I've been trying to get rid of it for a couple years now but unfortunately ;have probably only been making it stronger! My plan is to cut it down when it's flowering before any more seeds fly off it and maybe put some kind of weed barrier cardboard or something then dirt on top and plant right over it! What do you think? Or maybe i should just dig out a bunch of the dirt roots and all and put a huge layer or cardboard the dirt and plant over it!!

I can't post a picture right now because it's still under the snow! Just preparing for the time ahead.....Maybe i should put up a pretty sign :) Welcome to my weed garden where thistles thrive and choke out everything else i try to grow! I know it is bad for the environment but i am also considering the cutting after flowering and using a little round up on them too....

I used to own a crafters' mall and made quite a bit of money making pretty signs! The sillier the better.

I would rather use a lesser amount of roundup now than more later. My next door neighbor had all of their planting beds taken over by Canada thistle. They had to kill everything to get rid of it. Beautiful beds now empty. Lots of herbicide! I don't know about burying the weed barrier with dirt on top. You will get other weeds coming up in the dirt and they won't get blocked. Bits of Canada thistle root can grow to make more plants. Never let it go to seed. You can cut it while flowering then let it flower again and cut it before it goes to seed. That will weaken it. Using herbicide in the fall is a good time since plants are sending energy (and herbicide) to their roots.

Keep in mind that the World Health Organization (WHO) has determined that the glyphosate products are carcinogens.

http://sustainablepulse.com/2015/03/26/who-glyphosate-report-ends-thirty-year-cancer-cover-up/

kimmq is kimmsr

They used the word probable in there.

okay so I'm gonna go with digging out a bunch of dirt, doing the cardboard dirt on top then plants, if i get other weeds i can deal with those but the thistles are the ones that just dont go. if that doesn't work i might make that area into some sort of raised bed instead.....

I suspect you will find (have found) that thistles, with their robust root system, will simply grow through any mulch.

Old post so posting for future visitors

Sorry for the late response, but if you're still needing to deal with this in the upcoming season (or for new people to this thread), I found a solution that works here in western Washington. 20% acidic vinegar does the trick (https://www.ars.usda.gov/news-events/news/research-news/2002/spray-weeds-with-vinegar/).

This is much stronger than household vinegar. I found online: https://www.factorydirectvinegar.com/?gclid=CNWfk4W7g88CFU9qfgodxrYPnw, but if you live in a larger city, you might be able to find it locally.

This is caustic stuff, so be careful! Wear gloves and eye protection, do it on a sunny day of about 70 degrees or more, non-windy day, no chance of rain, etc. I do it when I know the neighbor kids are at school - there's no fence dividing our yards. If you cover the whole plant, they say it goes into the root to kill it. One particular thistle I did this to, has had no thistle growth in that spot yet - and it had a good amount of hot weather to come back up again. We'll see what happens this season in that spot.

From everything I read, tilling Canada Thistle only makes more thistles - by sprouting new ones from all the broken pieces. And this vinegar doesn't seem to work as well on other weeds.

Good luck!