Onions are members of the Allium genus, and there are more than 700 species. They are one of the oldest and most important plants to be cultivated as both an herb and a vegetable. Their sulfur compounds give them their unique smell, and also make them beneficial to digestive, circulatory, and respiratory systems. Onions are hardy plants that thrive in climates Z4-Z9. Hollow, semi-circular foliage sprouts one to two feet tall above the bulb. Members of the Aggregatum Group, such as the shallot, produce clusters of smaller bulbs rather than one single large bulb.
Onions are easy to grow and require fertile, well-drained soil. They can be propagated by seeds, transplants, or small bulbs known as sets. For the home garden, planting sets is the easiest and fastest method. For best results, carefully plant sets with the stem end up and cover with a quarter-inch of sifted compost. Allow about six inches between sets and about a foot between rows. A one-pound bag of sets will plant about a 50-foot row. Plant onions as early as possible in the spring. They require full sun. The time it takes for bulbs to mature is a result of the amount of sunlight it receives rather than plant maturity. On the average, a set matures in about 100 days.