Onion Types: Long-Day or Short Day?
Almost every gardener I know buys onion starts in the spring and gets them in the ground as much as a month before the first frost. It’s true that some of our friends living in more moderate climes will stick onions starts, if they can find (or grow them) in the ground in the fall, mulch heavily, and keep their fingers crossed. My experience tells me that onions don’t do well with hard freezes and that making it through the winter depends on luck and how well insulated you can keep the young plants.
I’ve also known a gardener or two who go to the trouble to start their own onion seed, both indoors and out. The reason they do this is selection. While most nurseries carry only a few (if more than one) types of onions ready as sets, buying seed allows you to choose your favorite tasting varieties, often not available as set. And it gives you a chance to make sure you have the right onion for your location on the planet.
It’s common for beginning gardeners not to know the difference between long-day and short-day onions. I didn’t when I was a green-horn gardener. And usually nurseries supply only sets that will work in your area. So ignorance in this regard may still result in bliss. But it’s important to know the long-day, short-day difference when you’re starting your own onions from seed.
Sowing onion seed directly in the garden works best in places with a longer growing season. This usually means planting short-day onions, those that don’t require as many hours of daylight. Why? Generally — and don’t forget, altitude plays a part in this — warmer climes are usually below the 35th parallel of latitude which mean fewer minutes of sunlight each day than places further north. You’ll want to plant long-day onions if you live above the 35th parallel, a line that generally divides the American south from the American north.
Long-day onions are those that require 14 and more hours of light (measured around the equinox, June 21). Here in Bozeman, Montana, long-day onions are the rule. In Macon, Ga? Short-day onions like the Red Creole or Texas Early Grano.
There are also intermediate onions — those that require around 13 to 14 hours of sunlight to set bulbs. These include, at the lower light requirement Early Yellow Globe, Australian Brown, White Portugal and Southport Yellow Globe ; and Red Wethersfield, Southport Red Globe, Italian Red and Flat Madiera at the upper, somewhere over 13.5 hours of light. Intermediate onions give growers near and above the 35th parallel options that can mean the difference between plump, wonderful onions and results that, well, might be less than anticipated. Some onions, like Golden Princess give results no matter where they’re planted.
What happens if you plant the wrong onion in your particular area? Poor growth that doesn’t produce bulbs. Most onions bought in sets are of the long-day type (unless you live in the deep south) and are suitable for growing in most parts of the country. But make sure — before you plant– you have the right onion for your north-south location.