Collecting lupin seed is easy. Mine is not quite ready yet. The picture below shows a lupin plant producing seed. I usually let the pods get a little bit browner & drier before I harvest.
When the seed pods look like the photo below, it is time to harvest the seeds . . . pull off each of the pods, and let dry on a screen or plate. when seed pods are fully ready they will crack open easily. careful they will do that naturally in your garden if you don't get to them in time.
if you look closely, you can see the dark brown seeds in the pods
& finally, when you hear that rattling sound, and the pods are mostly brown, your seeds are fully ready to harvest!
Let dry, store in a dark & cool place until the Spring!