tree onion (or proliferous/top/Egyptian onion), either a variety (var proliferum) of Allium cepa or (as in Cornucopia) A. cepa × proliferum. Perversely, the best-known strain is called the Egyptian onion. This plant, which is a hardy perennial, spreads itself in an odd way. The flowering top of the plant, which may reach a height of 1.2 m (4') or more, develops into a cluster of bulbils (miniature bulbs); and above these may develop a ‘second storey’ of more bulbils. As they grow, their increasing weight and the withering of the stem causes the cluster to keel over and plant itself at some distance from the parent plant. The underground bulbs also divide like those of aggregate onions. Both top bulbs, picked before they fall, and the underground ones are eaten. They are hot and strong. The little round top bulbs make good pickled onions.
