The Brassicas, also called Cole Crops or Cruciferous Vegetables, include crops like mustard, cabbage, broccoli, kale, boy choy, rape and MANY more. But if allowed to bloom, they usually make sprays of cheery yellow flowers (daikons are usually pinky-white) followed by the archtypal long slender seed pods also arranged in sprays. The trick to saving their seeds is to let the pods get ripe and tan, then cut off the seed spikes BEFORE the pods begin to shatter. I like to dry the severed spikes in a brown paper bag for a couple weeks, then use my hands to shatter the pods. You can wind winnow away the chaff out doors or, depending on the size of its holes, use a kitchen colander to strain the chaff out of the seeds into a bowl below. Pour them into a paper envelope, label, like "Green Wave Mustard" 2010. I also like to right on the envelope what brassica it grew close to as the Brassicas can be wildly interfertile. For instance, the pics of blooms and seed spikes are of a seedling that popped up last August in a baby pool Water Wise Container Garden that was OBVIOUSLY a cross between Purple Kozaitai and Mizuna. Since no other Brassicas were in bloom at the time, these blooms should be self-pollinated and seedlings next fall could show wild variation next winter due to genes from ancestors activating, just like a blond man and woman can have kids with red or dark brown hair....grandparents and great-grandparents' traits could show up! Here in Tampa, the Brassicas set seed in spring and early summer...in cold climates expect the seed clusters in the autumn. Give it a try...not much work, can save you money as regards buying new seeds, plus seeing what emerges from the seeds (in Denver I had spontaneous crosses between Daikon and Purple Top Globe Turnip appear!) can be fun.