It goes by many names the most common being Egyptian Walking onions.  They are fully hardy and perennial at least to zone 3 .  The scientific name allium cepa var. proliferum leads one to believe that they are prolific…and they are. You will have plenty to share by next year, however I would not call them invasive since they are extremely easy to remove if you have too many and should then be eaten. These onions can reach 3 feet in height.  The curly and unusual shaped onions on the top are downright weird. They are sure to be a conversation piece in your vege or herb garden.  Both the top sets and the offsets at the bottom of the plant are edible.