Allium cepa L., or the garden onion, is not the sweetest smelling flower in the lily family, and has been accused of bringing some of us to tears. The allium genus of the liliaceae family, however, contains some very tasty members that are staples in many cuisines the world over. Onions are part of the mirepiox (celery, carrots and onions) in traditional French cuisine, as well as the "holy trinity" (bell peppers, onions, celery) in Cajun cuisine. Used raw and cooked, onions and their relatives lend their flavors to many popular dishes.
Chives (Allium schoenoprasum L.) are like other plants in this family, a bulb plant. However, they are most known for their tender green tops. The tapered delicate leaves have a mild onion flavor used in salads, as a topping on potatoes and even for garnishes. They can grow in the wild and are native to the lower 48 states as well as Alaska and Canada.
Looking like overgrown spring onions (or scallions), leeks (Allium porrum L.) have the traditional onion flavor, but are somewhat milder. Grown best in somewhat sandy soils, leeks usually need thorough cleaning to remove the sandy grit before using. Typically used cooked, they are occasionally used in salads, though they tend to be dryer than other members of the onion family are.
Shallots (Allium cepa var. aggregatum) look like a small version of the common onion, but technically they are different; they grow in clusters, unlike onions which produce single bulbs. They have a mild onion taste, and they are often used in sauces, salad dressings or raw in salads.
As widely known as the onion, garlic (Allium sativum L.) is used in cuisine all over the world. Garlic grows somewhat like the shallot, in tightly grouped clusters. An entire cluster of garlic bulbs is called a "head" of garlic, with each individual piece being a "clove". The taste is more distinctive than other allium family members and is much stronger. It is generally used in smaller proportion, especially when used raw. When roasted and cooked, garlic mellows significantly, lending a somewhat sweeter taste to this pungent bulb.
Scallions (Allium fistulosum) are also known as green onions, spring onions or Welsh onions, depending on where you are from. They have a similar design to leeks; however, the green leaves are hollow. This particular variety will not develop a bulb. Scallions have a taste that is very similar to garden onions, but a little milder. They are most commonly used raw, as their more delicate composition and taste does not hold up as well when cooked.