I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
When it is no longer pretty you can cut off the bloom head just below the bloom. Once the foliage on the stalk starts to yellow you can cut it back to near the ground line.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
Q&A Library Searching Tips