I always cut off the stalk once the flowers have died so have never seen a seed head develop. If you do try to propagate from the seeds, let us know how you get on!
My Amarillo’s was very late flowering this year but was enormous and beautiful when it did when it was over I put it out to the shed to dry out and just noticed it has a big full seedhead I ve never had that before and was wondering if anyone had grown from seed and when and how ? Thanks