Tree onion

Tree onion
Onion stalks with bulblets, or miniature onions grown at the top of the stalk.
Scientific classification
Kingdom:	Plantae
Clade:	Angiosperms
Clade:	Monocots
Order:	Asparagales
Family:	Amaryllidaceae
Subfamily:	Allioideae
Genus:	Allium
Species:	A. ×proliferum
Binomial name
Allium ×proliferum (Moench) Schrad. ex Willd.

Tree onions, topsetting onions, walking onions, or Egyptian onions, Allium ×proliferum, are similar to common onions (A. cepa), but with a cluster of bulblets where a normal onion would have flowers. Genomic evidence has conclusively shown that they are a hybrid of the common onion and the Welsh onion (A. fistulosum). However, some sources may still treat the tree onion as A. cepa var. proliferum or A. cepa Proliferum Group. Tree onion bulblets will sprout and grow while still on the original stalk, which may bend down under the weight of the new growth and take root some distance from the parent plant, giving rise to the name "walking onion". It has been postulated that the name "Egyptian onion" is derived from tree onions being brought to Europe from the Indian subcontinent by the Romani people.

The phenomenon of forming bulblets instead of flowers is also seen in garlic and other alliums, which sometimes may also be referred to as top onions or tree onions. The bulblets are usually marble-sized, between 0.5 cm to 3 cm in diameter.

Many tree onions are very strong flavoured, although some cultivars are relatively mild and sweet. The underground bulbs are particularly tough-skinned and pungent, and can be quite elongate, like leeks, or in some types may form bulbs up to 5 cm across. Young plants may be used as scallions in the spring, and the bulblets may be used in cooking similarly to regular onions, or preserved by pickling.

Gallery

• Allium cepa2.jpg

  Egyptian onions

• Sint Jansui (Allium fistulosum var. bulbifera).jpg

  Tree onion

• Egyptian Tree Onion, Walking Onion, Topset Onion (Allium cepa var. proliferum).jpg

  Growing in a garden