Tree onion

The tree onion (''Allium'' × ''proliferum'') is a perennial plant similar to the common onion (''A. cepa''), but with a cluster of bulblets where a normal onion would have flowers. Tree onions are also known as topsetting onions, walking onions, or Egyptian onions. Genomic evidence has conclusively shown that they are a diploid hybrid of the shallot 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. The bulblets are usually marble-sized, between 0.5 cm to 3 cm in diameter. They 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" derived from Romani people bringing tree onions to Europe from the Indian subcontinent.
The phenomenon of forming bulblets ( bulbils) instead of flowers is also seen in top-setting garlic and other alliums, which sometimes may also be referred to as top onions or tree onions.

Also known as turfed stone leek, it may be cultivated commercially and for foliage. It is described as a shallot which can be grown in tropical conditions.

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.

Culinary use

Japan

The plant is known as in Japan. Considered a specialty of the Hiroshima Prefecture, it is used in local cooking similar to other scallions.

Korea

In Korea, ''Allium'' × ''proliferum'' along with '' A. fistulosum'' is called ''pa'' (, "scallion"), while common onions are called ''yangpa'' (, "Western scallion"). While ''A.'' × ''proliferum'' is called ''jjokpa'' (), ''A. fistulosum'' is called either '' daepa'' (, "big scallion") or '' silpa'' (, "thread scallion") depending on the size. Unlike ''daepa'' and ''silpa'', which are usually used as a spice, herb, or garnish, ''jjokpa'' is often used as the main ingredient of various scallion dishes in Korean cuisine. Common dishes made with ''jjokpa'' include '' pajeon'' (scallion pancakes) and '' pa-kimchi'' (scallion kimchi).

File:Haemulpajeon.jpg, '' Haemul- pajeon'' (scallion pancake with seafood)
File:Scallion kimchi.jpg, '' Pa-kimchi'' (scallion kimchi)

Gallery

Image:Allium cepa2.jpg, Egyptian onions
Image:Sint Jansui (Allium fistulosum var. bulbifera).jpg, Tree onion
Image:Egyptian Tree Onion, Walking Onion, Topset Onion (Allium cepa var. proliferum).jpg, Growing in a garden

See also

* List of'' Allium'' species
* Scallion

References

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proliferum
Interspecific plant hybrids
Korean vegetables
Onions
Perennial vegetables