Well, Im not exatly sure what stone soup thistle are, but if they are the thistles with only one flower and the big purle one I remember going to Ireland 5 years ago and they were everywhere, the irish thought they were a common weed in their mind and tried to iridacate it from any garden space, but Ive always been fond of them. But they are biennals so yea, if you wanted to you probable could keep ahead of them.

Stone Soup Farm was in Monroe. Saw those giants myself about 10 to 15 years ago. What ever happened to the place? Remember it being a little pricey and back to earthy.
Onopordum acanthium (Scotch Thistle)

Here is a link that might be useful: A little info about Scotch Thistle

Stone Soup Farm was sold a few years ago and is now a private home and garden.
The woman that use to own it has moved to one of the coastal towns and now has a garden shop I believe? My sister went to it, I'll have to ask her about it. We did get to the place before it was sold, it was a lovely place!

Cathy

Thanks, everyone! I'd love to know about a garden shop that is owned by the woman who used to own "Stone Soup" in Monroe. Cathy, please let me know if you find out the name and location. And yes, I believe that the thistles that I just called "stone soup thistles" are really Scotch Thistles, and I found a source of the seeds and plan to grow some.
This was very helpful. Thanks again to everyone who answered!
Dottie