Since there are three types of onions, you need to understand them and consider where you live. Different types of onions like a certain amount of daylight to form a bulb. Technically, you can grow all three types but if you want a full grown bulb you will need to consider the following:
Long Day Onions enjoy about 14 or more hours of daylight in order to start bulbing. This type is great for growing in the north in zones 6 or colder. If you live in the north, you should plant them in early spring and harvest them in the summer. Also, this type stores the best.
Intermediate or Day Neutral Onions enjoy about 12 to 14 hours of daylight to start the bulbing process. This type is great for all regions. Just like long day onions, you should plant intermediate onions in the early spring if you live in the north. Just like short day onions, you should plant intermediate onions in the fall if you live in the south.
Short Day Onions enjoy about 10 to 12 hours of daylight to start bulbing. This type is great for growing in the south in zones 7 and warmer. If you live in the south, you can plant them in the fall and harvest in the spring. This type of onion is sweeter and better for harvest to table.
If you need some onion varieties to grow, check out the features of Ringmaster Onions and Red Amposta Onions.
