As a gardener, “types of onions” refers to whether the onion is a long-day, intermediate-day, or short-day type. Each of these types contains multiple varieties. To choose which onions to grow in your garden, consider type first.
In order to get onions to form bulbs, the day length has to be long enough to trigger the onion to switch from growing large green tops to developing its bulb. Different types of onions have different requirements in terms of the length of day needed to trigger this switch from top growth to bulb growth. Since day length is related to latitude, the best type of onion to grow in your region depends on how far north or south you are. (See the How to Grow Onions article.)
If you try to grow a long-day onion in the south where day length is shorter, it will never form a bulb, no matter how long it grows. You must choose the right type for your latitude.
Now when a cook considers “types of onions” they may be thinking, “Do I want to use 'Walla Walla Sweet', 'Bermuda', 'White', 'Cippolini' , 'Torpedo' or 'Yellow' onions in this dish?” In this case the cook is considering different varieties, not types.
Unless that cook is also a gardener, they would have no reason to consider
type, only whether the onion is sweet, pungent, mild, strong, juicy, crunchy etc.
Here is a chart showing a few of the different varieties that are available by type. There is some overlap (in other words, some varieties may bulb at shorter day-lengths than indicated). Check out the different seed catalogs for more choices.
Long-Day Onions (need 14-16 hour days)
Red Candy Apple
To learn more about growing onions, visit these related pages:
How to Grow Onions
Onions need soil that is loose and evenly moist so that they can easily push it aside when they start to form bulbs. This is the main how-to article that describes the best soil conditions, how day length affects bulb growth, fertilizing correctly, and how proper watering can prevent disease.
All about planting onions: how deep and how far apart to plant, the difference between growing from seed, onion sets or onion transplants, and when to plant onions for maximum bulb growth.
Growing Onions from Seed
There are some advantages to starting your own onions from seed, but you’ll need to start them indoors in order to get a jump on the season and give your onions enough time to develop bulbs. Find out how and when to plant, and when to transplant outside.
Most onion diseases are a lot easier to prevent than to cure. Learn 5 ways to prevent onion diseases, and find out what to do if your plants do become sick.
Onions will send up a flower stalk if they become stressed, which takes energy away from growing nice large bulbs. Learn how to prevent onion bolting, and what to do if onions do start to go to seed.
Make sure to wait for harvesting onions until the tops start turning brown. Learn the proper way to harvest and cure onions for the most successful winter storage.
There are several cool and clever ways to store onions, but the most important things are to provide excellent air circulation and to keep them dry. Read about tips and tricks for storing onions.