‘Which type of onion should I plant’ is a question for which there is no quick answer. If you’re thinking about growing onions and not sure which variety to choose, it’s best to start by understanding some basics about onions. So read on, friends, for a primer on onions. And get some guidance about which ones are best for you and your specific growing situation.
Which type of onion should I plant? The three types
There are three types of onions grown for bulbs. They are short-day, intermediate-day, and long-day onions.
These three types each give us an idea of the amount of daylight needed for the onion to start producing its bulb.
Short-day varieties start producing their bulbs when they receive between 10 and 12 hours of daylight. Intermediate-day varieties need between 12 and 14 hours of daylight. And long-day varieties need between 14 and 16 hours of daylight to start growing their bulbs.
So how does one figure out the amount of daylight they receive?
Use Your Area as a Guide
We know our days are either getting longer or shorter, depending on what part of the year we are in. In the northern hemisphere, the days start getting longer around the 21st of December. Each day thereafter receives more daylight until around June 21, which is the longest day of the year. Because the northern hemisphere is tilting towards the sun during the winter months, the furthest northern states actually receive more daylight than southern states.
Because the states to the south receive the fewest hours of daylight during the growing season, they should plant short-day varieties. If they try growing a long-day instead, it would never produce a bulb. It just won’t receive the necessary hours of daylight to “switch on” its bulb production.
Because they receive the most daylight during the growing season, northern states should plant long-day varieties. These include the Copra onion or Yellow Sweet Spanish onion. If they try growing a short-day variety, it would receive too much daylight before its leaf growth had finished. Which would result in a very small bulb.
The states in between should grow the intermediate-day varieties. Depending on which mid-states, some short- or long-day varieties might grow well, too.
Now that ‘which type of onion should I plant’ has been answered, are you ready to get growing? Then check out our selection of organically grown onion plants. And for complete onion growing instructions, see How to Grow the Most Flavorful Onions.