After your daikon flowers fade, seed pods will form. They will be green at first, but then turn tan as they dry. You can harvest the pods as they fully dry, but I find it easier to harvest the whole stalk, pods and all, once the whole thing is dry. Radishes do cross, so if you have any other varieties growing nearby (1/2 mile) the seed may not be true to type. Hope this helps!
Oh my, how interesting! Have no clue about other radish-type creatures within radius. I don’t have any other radishes at all.
I’ll plan to let it go to seed then. When you say, “harvest the whole stalk” are you also referring to the root?