Broccoli is most often treated as an annual but overwintering varieties can be allowed to
flower and set
seed the following
spring and summer. For annual broccoli, an early
spring sowing is recommended. Broccoli is normally cross-pollinated by bees, so it is best to grow only one variety or isolate two or more varieties considerably. Broccoli, as a member of the Brassica family will cross with cabbage, Brussels sprouts, cauliflower, collards, kale and kohlrabi, so must not be flowering at the same time as any of these. (Which is unlikely to happen unless you are also saving
seed of one or more of them.)
As for other brassicas, broccoli
seed is borne in narrow pods. Harvest when pods are dry and brittle.
plant stalks can be laid on tarps or canvas for further curing outside or branches of pods can be placed in open paper bags and dried in the sun. Threshing can be done by hand, flailing or by rubbing the seedpods gently through screen. We normally snip the
seed stalks and immediately thresh them by foot in our box