Onions are one of the most important crops on a direct market farm, and it behooves you to learn to grow them well. What’s so great about onions? They can be sold at virtually any stage of maturity, they give you some leeway about when to harvest them, they don’t have to be thrown in the compost if you don’t sell them at market, and they can be stored for sale during the lean months.

But they’re not necessarily the easiest crop to grow. There are a few things you need to know about onions if you’re going to make them a major income producer.
The first consideration in growing onions is the staggering number of types. There are scallions, bulbing onions, red, yellow, white onions, long day, short day and intermediate onions, sweet onions and storage onions. (Not to mention all the related alliums such as leeks and shallots.) For the most part, choosing varieties is a matter of choosing a few within each type, so that you can be selling them over a long season.

The first onions to harvest are the scallions or green onions, which are non-bulbing onions ready for harvest in about 60 days. That’s simple. With the bulbing onions, though, day length becomes the determining factor in when and whether they bulb.

The general demarcation between short day and long day onions is the 36th parallel, which runs through Raleigh-Durham, NC, Nashville, TN, Fayetteville, AR, Stillwater, OK, the Grand Canyon, and midway between San Francisco and Los Angeles. South of that line, in summer, short day onions are grown that require 10 to 12 hours of daylight to bulb. North of that, long day varieties are grown that begin to bulb at 14 to 16 hours of daylight. In addition, there are day-neutral varieties that can be grown anywhere.

Within each day-length category are sweet or summer onions, which need to be eaten fairly quickly, and storage onions which can be held for longer periods of time. Some examples of sweet onions are the famous Walla Walla onion, a long-day type grown in the North, and the Granex type, short day hybrids grown in the South. Vidalia onions are not a single variety, but are any variety of the Granex type. A federal law says you can only call them Vidalias if you grow them in a certain region of Georgia. You can tell your customers your Granex onions are as sweet as Vidalias, but you can’t call them Vidalias.

After the sweet onions have been sold, you can start selling the storage onions, which are much harder and usually more pungent.

The Johnny’s Selected Seeds commercial catalog does a good job of sorting through all these different types of onions. If you don’t have the commercial catalog, get one by calling 207-437-4395. Check with your local Extension office to see if there’s any recent variety trial information for your area. You might want to grow some of the old standbys that perform well in your area, but also experiment with some of the new ones. There are plenty of exciting new onion varieties on the market.

Starting seeds
Check with Extension if you don’t know when to plant onions in your area. This is important because of the day length considerations mentioned above and because planting too early can cause bolting. Onions are technically biennials, which means it takes two years for them to go from seed to seed. If the young plant goes through alternating warm and cold periods, it may “think” it has completed two growth cycles and send up a flower stalk, effectively ruining the bulb below.

The best onions are grown from seeds, rather than sets or transplants. Seed-grown onions are less susceptible to bolting. In general, onions should be seeded in the greenhouse or under lights 12 to 16 weeks before the frost-free date, and planted in the field four to six weeks before the frost-free date. They will germinate in cool soil – as low as 45°F, but best germination is on a heat mat at 75°F.

Some people grow onions in soil blocks or cells with three to five seeds per cell. The clumps of onions are then planted together in the field, and they push apart as they grow. Others prefer to seed the onions in lines in flats, and separate the plants into singles when they transplant into the field.

Jan Dawson and Andy Reinhart of Jandy’s in Bellefontaine, Ohio, grow about 3,000 pounds of onions every year and start them all under lights in their house. Beginning Feb. 1, they seed the onions in foam trays full of potting mix, with sand added to loosen it. Jan says the roots are huge and healthy by the time they pull the plants for transplanting. The plants at that point, however, are still quite small – thicker than the lead of a pencil, but not as thick as a pencil, she says.