You may find some field guides that say bull thistle cirsium vulgare (or some other plant you have to boil and drain 3 times so you don't choke to death or die) is edible. Great! I am picturing a wonderful wild salad or soup now! I don't want to diss any of the field guides, but to say that the thistle "Provide palatable dishes" OK, but at what price?
You can really separate the writers who have actually done it, from the copy and repeat type writers when you come across talking about how GREAT bull thistle is to prepare and eat (it tastes so wonderful, it's so easy, here are 10 recipes for your enjoyment!! blah blah blah).
I mean really, have you ever seen or touched one of these babies?
Come on, by the time you get past all the thistles (and get poked a few times in the process), skin and eat the thing you could have built a really nice green house and grown some real salad food.
Don't get me wrong, I am SURE there is someone out there that will insist that it is the best thing EVER.
I doubt they have a newborn and toddler alongside when they are picking it.
Just a thought
PS- I am thinking the bull thistle has all of this protection for a reason, it must serve a much bigger and better purpose than for us to eat it as food. Considering all the other wild foods there are to choose from, I will let thistle be and enjoy it's lovely purple flowers:)