You can cut them anytime before it gets cold, but it's best not to let them get too mature. Because they are so fleshy, they need to dry in the warmest place you have. You can tie a brown paper bag ( don't use plastic) around the blooms before hanging them upside down-that way, the seeds can be saved for next year.

Thanks for the reply. Told me everything I needed to know.
Kim

You're welcome. One more thing-if I have a lot of blooms to dry in a hurry, I use my car's back seat-I run a string from one of the hooks to the other, rubber band the bunches, and hang them from the string with unfolded paper clips. I also cover the seat w/ an old sheet to catch any debris.