Allium cepa var. proliferum - prolific & reliable once they get established. Ours produced so many bulbils last year that their garden space was becoming overcrowded & I had to send 6 packages of bulbils to my cousins and friends. We've had them for a very long time, in fact my maternal grandfather who passed away before I was born was the original source. I use them in cooking, either the green tops or the largest bulbils as a sub for shallots. I once saw a garden with an 'onion ring' planted using the topsetters.