As I mentioned in another thread, I left the scapes on one plant of each of my three varieties this year to harvest bulbils. Yesterday I noticed that every time I bumped into the stalks, bulbils would start raining out of the flower heads, so I got a few bags and knocked all the bulbils off into them.
Today I realized there was no reason to leave the plants in the ground and pulled them. I was expecting small and possibly rotting heads to come up.
Boy, did I get a surprise!
Someone here had mentioned leaving heads in the ground longer to let them get larger and then as they will have no wrapper, use them for planting stock. I guess it works, even if you leave the scape on and harvest bulbils!