Answer: You should dead head them if you did not harvest the flowers for cut flower use. Allow the stems and foliage to continue to grow. When frost knocks them down and turns them brown, dig them up carefully. Clean them and allow them to dry for several days, discard any very small or damaged ones, and then store the rest in a cool (well above freezing) dry location for the winter in a cardboard box or paper bag.
Q&A Library Searching Tips