Onions have been grown for over 5,000 years, making them one of the oldest cultivated plants. They are also one of the world's most popular vegetable; Americans eat an average of 20 pounds of onions per person every year. They're also easy to grow, and there is a huge variety out there beyond your standard yellow cooking onion.
Starting Onions from Seed or Sets
Onions can be started from seed indoors 6–8 weeks before you plan to plant them outdoors; they can also be sown directly in the garden once the last frost date has passed. When sowing onion seed, sow them one to two inches apart. If you'd rather not start from seed, sets of starter onions can be purchased from catalogs and garden centers and planted in spring.
Bunching onions, or scallions, are usually started from seed sown directly in the garden. They are quick to mature, so it's a good idea to make several smaller sowings two weeks apart from spring to mid-summer for a regular harvest.
Growing Organic Onions in Your Garden
Onions should be grown in full sun, in fertile, moist and well drained soil. Onions need plenty of water, but they'll rot in very wet soil. Keep the area well weeded, since onions don't do well in competition with other plants. A two to three inch layer of mulch will conserve moisture and keep the weeds at bay.
You don't need to relegate onions to the vegetable garden. Their foliage is often quite pretty, and works well in a mixed border. They also work well in container plantings.
All onions can be harvested and used as needed throughout the season. For green onions, pull up onions that need to be thinned, or just pinch back the tops if you want the bulbs to mature. It will send up new leaves, and you can keep harvesting them, as long as you do so sparingly.
Bulb onions that you've grown for storage are ready to be harvested when the leaves start to turn yellow and flop over and the tops of the bulbs are visible above the soil line. They should be pulled up and allowed to dry for a few days before being stored in a dry, cold, frost-free place.
Onion Problems and Pests
The most common problems you'll face when growing onions are onion maggots and rot. Rot is most common, and is caused by excessive watering and/or soil that doesn't drain well. Onion maggots burrow into the stems, eventually killing the plant. To avoid this problem, make sure not to plant onions in the same place two years in a row.
Types of Onions and Recommended Varieties
Bulb onions, Allium cepa, form clumps of cylindrical foliage and develop large, round or flattened bulbs. Bulb formation is day-length dependent; if you live in zone six or lower, look for northern onion varieties that have been developed for long days. Bulb formation begins when days are sixteen hours long. Recommended bulb onions include:
- 'Candy,' an extra-early, sweet variety.
- 'Redwing,' a very reliable performer and good storage onion, ready to harvest in 100 to 120 days.
- 'Walla Walla,' which produces large, mild, sweet bulbs with golden skins. It's not a good keeper, and should be used soon after harvest.
- 'Sweet Spanish,' is another sweet variety, but unlike 'Walla Walla,' it is an excellent keeper, ready in 110 days.
- 'Champlain' is another very early onion, ready to harvest in about 90 days.
Scallions (bunching onion), Allium fistulosum, produces clumps of foliage and small bulbs (or, depending on the variety, no bulb at all.) Once they are established, they'll provide you with green onions all spring and summer long. Recommended varieties include:
- 'Evergreen,' ready to harvest in about 60 days.
- 'Salad Apache' is a deep purple variety, ready in 80 days.
- 'Red Baron' is a later vareity, ready in 110 days. It produces high yields of red and green roots.
Shallots (A. oschaninii and A. ascalonicum) produce offsets, or clusters making up a head of multiple cloves, much like garlic. The skin color ranges from golden to red to gray, with white flesh. Shallots are firm and sweeter than other onions. They are also much smaller than a bulb onion, but larger than the root end of a scallion. Recommended varieties include:
- ‘Banana,' which is a long shallot with shiny, copper-brown skin, crisp flesh and a distinctive flavor, ready in 85 days.
- ‘Picador’ is a rounded shallot with pink skin, white flesh, and mild flavor. It's ready to harvest in 88 days.