We’re seeing lots of thistles in the pastures right now, and we got to get them before they get too big. Just last week, they were hard to spot. Now they are bolting and getting ready to flower.
We have good options on thistle but the real issue is timing. In the roseett stage, they are easier to kill. Once they shoot up a stem (bolting), they get more difficult to kill. Here is a good chart of common herbicides used in thistle and their effectiveness during each growth stage.