Onions are a staple meal ingredient for many folks, and most cooks make sure to always have fresh onions available. The addition of nutritious onions can easily enhance otherwise bland dishes without adding a lot of extra calories. If you like to cook with onions, you may want to try your hand at growing onions in your garden.
Onions have been highly valued and grown domestically for millennia. It has been found that the ancient Egyptians were growing onions along the Nile and they ate a diet rich in onions as they were building the pyramids. With further research, we may someday discover that the ancient Egyptians also created the first breath mints!
Onions can be grown from seeds, sets or transplants. When growing onions in a home garden, they are most often grown from onion sets. Onion sets are the tiny onion bulbs that are typically found in early spring in garden centers and sometimes even in supermarkets. When growing onions from sets, you won’t get much choice in onion varieties, as they are usually sold as generic white, yellow or red onions.
Onion sets will begin to sprout if they are kept in a heated, well-lit shop for very long, so purchase your onion sets early and store them in a bag within the refrigerator until you’re ready to plant. Often the onion sets are displayed in a large basket or bin, which allows you to choose your own sets. Choose firm onion sets and leave behind any that have sprouted or that are mushy or dried out and papery.
Now here’s the tricky part of choosing and growing onions from sets. Onion sets that are larger than a dime in diameter are more likely to bolt early and form flower stalks. If an onion plant produces a flower stalk, that particular onion will not store well, so plant the larger sets separate from the rest and harvest them early for green onions. However, the smaller sets will grow onions that will not only keep better in storage, but they will also grow larger onions.
If the little onion sets are round, they’ll grow up to be flat onions. If the little onion sets are long or shaped like a torpedo, they’ll grow up to be round onions. This is just one way in which growing onions is just the opposite of what you may expect.
Growing onions from seed or transplants is the way to go if you want to grow a specific variety, such as Bermuda or Walla Walla. If you want to grow onions that will store well over winter, it is best to start with seeds or transplants. But for a successful onion crop, you must choose a variety that will grow well in your area. Listen closely, because this is the other way in which growing onions is the opposite of what you may expect.
Onion varieties are divided into two categories, which are long-day and short-day varieties. Long-day onion varieties begin to form bulbs when they receive fourteen to sixteen hours of daylight, while short-day onions start making their bulbs earlier in the season, when there are only ten to twelve hours of daylight each day.
Folks who live in northern states will get better results with long-day onions, while gardeners in the South will have better luck with short-day onions. Onions that are grown in the South, such as Vidalias, will generally not perform well in a Northern climate, and long-day varieties for Northern climates may not form bulbs in a Southern garden. Short-day varieties may grow reasonably well in a Northern state if transplants can be set out very early in the spring.
You may be able to find onion seeds or transplants at a garden center. If your local garden center doesn’t offer onion seeds or transplants though, the seeds can be purchased from any number of seed catalogs and a few also offer transplants for sale.
If you plan on growing onions that will store well and you are starting with onion sets, plant the smaller sets an inch deep and allow two to four inches between each set. Individual rows should be at least a foot apart so you can walk and work between them. If the sets are planted only two inches apart, every other plant may be harvested early as green onions. This will give the rest of the sets room to grow a nice big bulb.
Onion sets and transplants can be planted in early spring. A light frost won’t hurt newly-planted sets, but if a late hard freeze is expected the tiny plants will benefit from being covered and protected from the freeze. A spell of very cold weather early in the growing season can encourage the plants to flower early, but the earlier the plants can start to grow the more time they’ll have to develop a large bulb. Planting early can be a bit of a gamble with Mother Nature.
Growing onions from seed is more time-consuming but can produce a crop that will store well, and you’ll be able to choose the specific variety you want to grow.
In warm Southern climates of Growing Zones 8 and 9, seeds can be planted directly in the garden in mid-autumn. Cover the seeds lightly with a quarter inch of soil and they should sprout within a week to ten days. By February the tiny onion plants can be thinned to two to three inches apart so the growing onions have room to expand.
In cooler parts of the country, onion seeds can be started indoors in flats in late February through the middle of March. When the green tops are about five inches tall, they can be given a haircut to keep them from growing too tall before being planted out. The little onion transplants may be transferred to the garden in early spring.
Onion seeds can also be planted directly in the garden in cooler climates as soon as the soil can be worked. But be aware that cold temperatures can encourage the plants to flower, so watch the weather and don’t plant them out too soon before the last frost date in your area.
While they are growing, onions will need sufficient phosphorus to produce a large bulb. Some growers include a dose of phosphorus in the row as they are planting the seeds or transplants, and more fertilizer is added monthly as a side dressing. Phosphorus is the middle number in the N-P-K rating for fertilizer, so look for a fertilizer where the middle number is the highest of the three.
The growing onions will also appreciate it if they don’t have to compete with weeds for nutrients. Keep the onion bed free of weeds by shallow hoeing.
If you are growing onions for green onions, soil can be slightly hilled around the plants to help them develop the long, white stems that are desired for green onions. But do not hill onions that are meant for storage as hilling can cause the necks to rot in storage.
Green onions may be harvested once their green tops are six inches tall or more. The youngest onions will be the most mild, and they will develop a stronger flavor as they grow larger. If you are growing onions for cooking, individual onions may be harvested as needed once they form a bulb. The entire crop is ready for harvest when most of the tops have naturally flopped over, generally in late July through August. Growing onions should be allowed to mature naturally. Do not become impatient and bend over the tops yourself as this will interrupt the natural growth of the onions and they will not store well.
Any onion plants that have flowered should be harvested and used immediately. Once an onion has flowered it will not store well, so use those first. When harvesting the entire crop at the end of the season, it is best to pull them in the morning on a dry day. Allow the onions to air dry right in the garden until late afternoon.
Then before the evening dew sets in, brush off any excess soil from the onions and place them on elevated screens or slats or tie the tops together and hang them in bunches in a dry, airy place. Be careful to keep the onions from touching each other. The onions will be completely dried and cured in two to three weeks. Do not peel the onions until you are ready to use them in the kitchen.
Once the onions are fully dry, the tops can be cut back to an inch or two, then stored in a cool dry place. Onions that have been bruised or cut and those that have green tops or thick necks will not store well and should be used right away. Check the stored onions regularly and discard any that develop soft spots.
Onions generally have few problems as they are growing. Insects rarely bother them, although root maggots can be a minor problem in northern climates. If root maggots attack the growing onions in your garden, move the onion patch to another area of the garden the following year. Onion thrips can also damage the developing plants but they can be easily controlled with garden insecticides or insecticidal soap.
Even though onion bulbs are growing underground, you can get an idea of how large those onions will grow just by looking at their green tops. Onions grow rings, and for each ring there will be a corresponding green leaf on the plant. And the larger the Word leaf is, the larger its corresponding ring will be. When you look at your well-tended onion bed and admire all the happily-growing onions with their lush green leaves, you’ll know that you can expect to harvest a terrific onion crop.