A non-chemical control for thistle (mentioned in the original post) is to simply cut it off at ground level and continue to cut it off as it tries to grow back. It must set seed and if you don't allow it to do so, it will eventually die off. This is how we addressed a huge population of Canadian thistle in our front field (frequent mowing). Thistle seed, however, remains viable for a couple years so this is a lengthy process. Seems it would work OK in a flower bed though, and you then don't have to worry about the effects of either a commercial pesticide or vinegar on your daylilies. And once the thistle is truly dead, the roots would decompose for added organics.
