V. Prickly issue: Does Milk Thistle Spread thru dense couch grass?

Tried growing some last year in my garden I thought was bigger till the milk thistle started filling out -- they grow huge & hugely thistley!  Thought I captured most seed heads, but got 8 or so coming up in beds. I'm in Canadian Rockies zone 5. we're having a cool year, thus far. Anyway, been making like compost pile mounds out beyond the garden to plant squash I don't want sprawling all over the garden. No problem, now they can sprawl over grassland. Wondering if milk thistle seed can take & overtake in dense couch grass?  Maybe, oughtn't even try finding out? Maybe it's invasive to the point of being illegal? I dunno! Much Thanks to anyone who does!  OgreNick     BTW, I'm surprised there's no medicinal herb section under Growies, not even cropped up in these medically challenging times -- huh!

Nick Dimitri wrote:BTW, I'm surprised there's no medicinal herb section under Growies, not even cropped up in these medically challenging times -- huh!

https://permies.com/f/9/medicinal-herbs

Medicinal herbs is in the kitchen section. I guess because it's more about preparation and uses. Growies is more about the growing part. Of course a thread can be in both.

Sorry I don't know about couch grass and thistles...