Latitude matters when picking onion varieties to thrive locally

For me, the garden is an outdoor classroom. Each year I embark on a new exploration, a new plant or cultural technique. I will run out of gardening years before I run out of summer projects.

This year it will be onions, an essential ingredient in two of our favorite recipes: Apple-Ring Chicken and Gingered Squash and Apple Soup. I like the idea of preparing these meals with onions that I grew, reaching into winter storage for onions that only get sweeter with time.

So which varieties will grow in Marjorie’s garden? I wish that I could grow Vidalias, the Texas Grainex onions grown to perfection in Georgia clay. I recall that as a boy I would pull one from the garden, rub it against the legs of my pants to remove most of the dirt, and then bite into it like an apple. It was just as sweet.

It requires Georgia clay to turn a Texas Grainex into a Vidalia. But even if I filled a raised bed with that dark red soil, I could not produce much of a bulb, for Texas Grainex is a short-day variety adapted to latitudes where onions can be planted very early, in January or February, produce new leaves for months, then begin to form bulbs in April or May when the days reach 12 hours in length. A Vidalia-type onion planted in Maine around the first of April would see 12-hour days too soon, try to bulb-up long before leaf growth sufficient to produce a large bulb.

For the latitude in which I now garden, I need to choose long-day varieties, onions that can be planted in April and grow leaves until June when our longest days trigger the transition from leaves to bulbs. But of the dozens of long-day onions, which do I want to try?

For long-term storage, many Maine gardeners say that you can’t beat Copra, a medium-sized, dark yellow onion, pungent but sweet and excellent for cooking. It has the highest sugar content of all the storage onions, becoming milder with time in storage. Marjorie has grown it and says it will keep for a year.

I will transplant field-grown starter plants of Copra rather than trying to grow my own from seed. The transplants will have a several-weeks jump on the season and on weeds, advantages that I hope will promote production of large bulbs.

For Maine gardeners who prefer red onions, the best varieties for storage, according to Johnny’s Selected Seeds catalog, are Ruby Ring, Red Bull and Redwing. You may have to start these from seed, however, at least as far as Johnny’s is concerned – they don’t offer field-grown transplants for these varieties.

For immediate use, not for storage, I want to try Walla Walla, a Washington state variety described by Johnny’s as a “juicy, sweet, regional favorite.” In Washington the seeds are sown in August and the plants overwinter in the ground; bulbs form the next spring and are harvested in early summer. In Maine, we have to settle for spring-planted seeds or transplants that don’t get as big but are still sweeter than any other spring-planted variety.

I will soon sow seeds of a white Cipollini onion called Bianca di Maggio. Cipollini onions are small, flat and disk-shaped with a very rich flavor, deliciously sweet when cooked. There are also red varieties, including Red Marble with a pungent flavor perfect for pickling or roasting, new last year.

Come spring there will be onions in Marjorie’s garden, a full bed of Copras, smaller plantings of Walla Walla and Bianca di Maggio. Next week: the culture, harvesting and storing of onions.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.