if the head has turned from orange(ish) to black its ready to be harvested. i usually just sprinkle the seeds in the ground as they mature(like right now) or i save some in a paper envelopes for trading or i mix them with moist sand put in a ziploc bag and store in the refrigerator over the winter for sprinkling next spring.

If you intend to collect the seeds, make sure you know what they look like. They are not very obvious and can easily be confused with other debris you shake from the seed head. The first time I started with the debris and threw away the seeds. No wonder I waited for weeks and nothing germinated. The safest way is to shake the seed heads on the ground in late fall and let them germinate on their own.

Don't forget to leave some for the goldfinches and other birds to eat. They look so cute on the flower heads. :)

Yes, once they have darkened to black you can harvest them. I just sprinkle them on the ground, but certainly you can store them as mentioned above.

Marie

I cut my coneflower back when they get so tall they begin to fall over. The flowers are usually still purple. If I hang the stems (with the seedheads) up to dry, will the seeds mature enough to harvest later this fall?

I think that is a good question. I don't really know for sure, but my educated guess would be that the flowers may not have been pollinated and / or the seeds would not have fully matured, before they dried.