I've the got prettiest pinkish purple tall cosmos that Loz sent me (I think) and knowing that they are annuals I'd like to save some seeds. Help please.

wait for the seed head to dry, thanks put a bag under the whole seed head and rub it. If it is the right time, the seeds should fall off easily along with some white fluff

thanks. We've had a bunch of rain so right now everything is soaking wet. We're expecting more rain. Hope the seeds don't get knocked off before it dries out a little.