Do your have pods on the tips of the thin stems coming off the bloom spike? It can take a while for the pods to fill out/swell with seeds. You might have to plan on buying some seeds. I'm just guessing but I imagine you will have to wait another month or two before the seeds will be ready to harvest and then shell and store in the refrigerator.

You would have to sow the seeds in cell paks of sterile soil mix inside under lights at around 70 degrees sometime in late August and keep them inside until the outdoor temps are reliably under 70.

Most people just buy new ones each fall and now you see why.

Oh, and your seedlings may not have the same colors or shape of your plants. I think they should be close but you never know - they could end up looking like their great grandparents.