Short Day, Long Day: Does It Make a Difference to an Onion?

As you work through a seed catalog and stop in the onion section,  you’ll be confronted with a choice between “short day” and “long day” types. So what does that mean and is one better than the other for our area?

This is a comparative term which refers to the approximate hours of daylight a variety of onion will need in order to start developing the bulb.  Short Day means about ten hours a day,  while long day means twelve hours or more. Vidalia, as in Georgia, is a short day onion.

Onions are considered a cool season crop.  In theory, short day types would be better suited to the South; they would mature before summer temperatures arrive and the threat of bolting arrives, sending up a seed stalk, that is.

The Walla Walla, as in Walla Walla, Washington, is long day variety, more appropriate to the north where somewhat cooler conditions prevail.  At least that’s the theory.

But of course plants don’t always go along with human theories.  Talking with a number of experienced vegetable gardeners, at least in our area it doesn’t seem to make much difference which type you plant.  The variety itself, in terms of sweetness, color, size and days to harvest, how and when you’ll plant them and how you’ll use them- green or as keepers- will have a greater impact on your success than just the long or short day label.

Article written by Glenn Palmer, Extension Master Gardener Volunteer.