Alliums
Onions, garlic, leeks, shallots, and their relatives
The aromatic vegetable base of nearly every cuisine on Earth. Alliums are rarely the main vegetable in a dish but are foundational to cooking — the onion in mirepoix, the garlic in soffrito, the scallion in stir-fry, the leek in cock-a-leekie soup. The category's role is to provide depth, savory complexity, and aromatic foundation; its members are used in nearly every preparation.
About alliums
Alliums are the aromatic vegetable base of cuisine — the layer of flavor that almost every savory dish begins with. The onion at the start of a stew, the garlic in a sauté pan, the leek in a soup base, the shallot in a vinaigrette. The cooking application is foundational rather than featured: alliums make other ingredients taste better rather than serving as the primary subject of a dish. The unifying property of the genus is sulfur chemistry. When allium cells are damaged by cutting, crushing, or chewing, an enzyme reaction releases volatile sulfur compounds that produce the sharp raw flavor and tear response. Heat application denatures the enzyme and transforms these compounds into sweet caramelized products — which is why an onion sweated slowly in fat produces a completely different flavor than the same onion eaten raw. The temperature and duration of cooking dictates the final flavor; this is why caramelizing onions properly takes 45 minutes to an hour at low heat, not 10 minutes at high heat. Cultivar specificity within the category is significant. Yellow onions are the universal cooking workhorse; red onions are sharper and used raw or briefly cooked for color; sweet onions like Vidalia have low sulfur content and can be eaten raw or used where mild flavor is wanted. Garlic varies in heat and sweetness based on variety and growing conditions. Shallots are not interchangeable with onions despite shared genus — finer flavor, less aggressive sulfur character, much better in raw applications. Leeks bring a milder, more sweetly aromatic character than onion. The cook who pays attention to allium selection produces better food.
Category profile
Member varieties
7 varieties in this category. Tap any variety for its full editorial profile.
Seasonal pattern
Dry-storage alliums (yellow onion, garlic) are year-round through curing and storage. Fresh alliums peak in spring and early summer — green garlic, scallions, ramps (wild allium, brief window). Sweet onions (Vidalia, Walla Walla) have short peaks tied to specific origins. Leeks peak in fall and winter.
Selection guidance
Dry-storage onions and garlic: firm, dry papery skin, no sprouting, no soft spots. Heavy for size. Sweet onions: same firmness checks; no soft spots. Fresh alliums (scallions, leeks): crisp white parts, no slime, fresh-looking green tops. Garlic: tight head with no separated cloves, no sprouting green shoots inside cloves (a sign of age). Shallots: firm, copper-skinned, heavy.
Typical preparations
Sweat onions in fat (oil or butter) over medium-low heat without browning to build sweet aromatic base (the foundation of most braises, soups, sauces). Caramelize onions: sliced onions in fat over low heat with patience, stirring occasionally, until deeply browned (45-60 minutes). Garlic: smashed and chopped fine for most cooked applications; minced for raw applications; whole cloves for roasting. Shallots: thinly sliced raw for vinaigrettes and pickles. Leeks: split lengthwise and washed (grit holds in layers), then sliced. Scallions: thinly sliced for garnish, or split lengthwise and grilled.
Editorial notes
Most US supermarket garlic is sourced from China — the price point reflects this, and the quality difference between Chinese commodity garlic and domestic California garlic or specialty hardneck varieties is meaningful. Hardneck garlic (rocambole, porcelain, purple stripe) has more complex flavor than softneck commodity garlic; it stores less well but cooks dramatically better. The garlic at the farmers market in summer and fall, just after harvest, is a different culinary product than the supermarket garlic that has been in storage for many months.