If you let one get past its prime, simply pick the petals off and use the brown cone in the vase. Don't throw the arrangement away when you're finished. Let the flowers dry completely and then scatter the seeds around for a denser planting. The same is true with purple coneflowers. More flowers are produced in the second and third years.
Purple coneflowers are perennials whose clumps can be divided in the fall when necessary.
This may not need to be done for three or more years. It also can be propagated from its own seed. After you grow Echinacea for a few years, you will wonder how someone could name such as pretty flower after a hedgehog. Recommendations on this web site do not endorse any commercial products or trade names.