Allium is a genus of herbaceous biennials or perennials in the amaryllis family (Amaryllidaceae) with over eight hundred species, mostly native to the Northern Hemisphere. Some, like star of Persia are popular garden plants while about others are edible and commonly used in cooking. The edible ones are harvested for either their leaf or bulb and include onions, garlic, chives, and leeks.
Allium bulbs are actually swollen layers of leaf bases containing the sugar fructose that causes the tissue to brown, become sweet, and caramelize when cooked. Allium leaves also contain fructose but in a much lower concentration and so do remain pale and less sweet in cooking. All alliums contain sulfides in their cells and become strong smelling when in contact with the enzymes called allinases, carried in separate structures in the cells. Cutting into the allium causes the enzymes to come in contact with the sulfides and the unique scent and flavor of alliums results. In addition, cut onions release sulfenic acid that breaks down into several compounds one of which is a volatile gas that stings the eye on contract.
Edible Alliums can be divided into two groups: those that are grown for their bulbs and those that are grown for their leaves. Here are fourteen of the most common edible Alliums with brief descriptions and use.
Bulb Alliums (Note: Many bulb Alliums are varieties or different stages of the common, yellow onion, Alium cepa)
Cipollini Onions (Allium cepa)
Small, flattened onions with papery flesh and high sugar content; Excellent for roasting or grilling
Elephant Garlic (A. ampeloprasum var. ampeloprasum)
Baseball sized with many cloves and white papery skin; not a true garlic but can be used like garlic, raw or briefly cooked
Garlic (A. sativa)
Golf ball sized with many cloves and white or purple papery skin; use raw or briefly cooked.
Pearl Onion (A. ampeloprasum var. sectivum but more commonly A. cepa)
Small (less than one inch diameter); white papery skin; boil, braise, or sauté.
Red Onion (A. cepa)
Red skin and white flesh tinged with red; color fades with cooking; use raw or cooked briefly
Scallion/Green Onion/Spring Onion (A. cepa var. cepa)
Immature onion; may have small white bulb or no bulb; less pungent than yellow onion; stem, bulb, and long green leaves used raw or briefly cooked.
Shallot (A. cepa var. aggregatum)
Small, muliti-bulbed; brown , gray, or rose red papery skin; green or magenta tinged flesh; dryer, sweet and more mild flavored than yellow onion; useful roasted or sautéed
Sweet Onion (A. cepa)
Large, slightly flattened; sweeter, more moist and less pungent than yellow onion; example is Valdalia; use raw.
White Onion (A. cepa)
Large, papery white skin; sweeter and more moist than yellow onion; can be used as all purpose onion.
Yellow Onion/Spanish Onion (A. cepa)
Golden papery skin, strong scent; common onion generally used for all purposes.
Chive (A. schoenoprasum)
Clumps of thin green leaves have mild flavor; use raw or briefly cooked.
Leak ( A. ampeloprasum )
Related to elephant garlic; dark green leaves have moist white root end that is usually preferred in cooking for its mild onion flavor; use simmered, braised, roasted, or grilled.
Wild Leak/Ramp (A. tricoccum)
A North American native with broad, smooth, light green leaves, a scallion-like stalk and bulb, purple root end, often with stems tinted with deep purple or burgundy; use cooked.