Radish will grow seeds ponds on at the top. I let mine grow till they turn brown and then pick some very large radishes and saved the seeds from the pods. It did take a long time. I planted them this year and they growing like crazy for me.

Happy Gardening,
Anna

The radish seed pods are also edible. By the time the radish produces seed pods the underground part isn't really edible unless you're really tough.