I decided to give the vinegar another try, and I must say, it certainly works better on hot days than it does on comfortable ones!! This is the patch in the middle picture from before; growing happily, largely unaffected by the vinegar. Not this time! Holy cow, what a remarkable effect, and in only a few hours. I kinda feel guilty at taking out all the happily growing plants like that. I really hate killing things, even weeds. Below them are before and after pics of what it does to thistles.