Opinionated Gardener: Onions: Of seeds, seedlings, sets and photoperiodicity

Onions – Allium cepa. It’s time to plant them… outdoors, that is. So, hurry, especially if you plan to direct seed them. If you are planting seedlings or sets, you’ve got a bit more time. But not much. That’s because onions are “photoperiodic” or “sensitive” to the length of daylight. For when the longest (15 hours) day of the year arrives in Maine on June 21 (1:46 am to be precise), the onions you planted from seed, seedlings or sets will start “bulbing.” No matter that the green tops have just begun to grow, ready or not, when the solstice arrives, top growth will stop and the bulb or bottom growth will start. It’s those big tops that will produce the bottom big bulbs.

While it may not be a matter of life and death to you as to how large the onion bulb you harvest this fall will be, it does matter to the onion. Onions are “biennial,” taking two years to complete their life cycle. They depend on the food stored in the bulbs the first year of their life cycle to produce flowers and set seed in the second year. The more abundant the food supply the greater the chance for setting seed. It’s a matter of sheer survival. (Some scientists have speculated that the bulb evolved as a way to store energy when climatic conditions for seed production were slim while waiting for a better time- next season to flower and set seed.)

Of long and short-day onions

While timing is important when it comes to growing onions, not all onions operate on the same biological clock. Some start bulbing when the daylight is 12 hours or less in length; some start bulbing when the daylight is 15 or more hours of daylight. If you remember your earth science, due to the tilt of the earth toward the sun in summer, the further north you go the longer the length of daylight; the further south you go the shorter. (It is generally accepted in onion bulbing circles that the demarcation line between north and south occurs at 36 degrees north of the equator. Maine stands at about 45 degrees north, with a maximum of 15 hours of daylight at the summer solstice.)

So it is not surprising that there are so-called “long-day” onions and “short-day” onions and that short-day onions if grown in the north will begin bulbing up too early and produce only small bulbs (not enough top growth) while long-day onions if grown in the south never even begin to bulb up (not enough day length). It’s got to do with light waves and special pigments or “phytochromes.” But the Opinionated Gardener is not going to go there; instead, she’ll go practical and focus on varieties that grow best here in Maine at 45 degrees, give or take a few degrees, north latitude.

For that, she turns to Johnny’s Selected Seeds. To ensure their customers nationwide are satisfied, Johnny’s indicates the optimum range in latitude where each variety in its catalogue grows best (sort of like a plant hardiness rating). Johnny’s offers several long-day varieties including “New York Early” (adapted to 38-50 degrees latitude) and “Red Bull” (adapted to 43-65 degrees latitude). Among its short day offerings are “Desert Sunrise” (adapted 30 to 36 degrees latitude) and “Pumba” (20 to 36 degrees latitude). But that’s not all; Johnny’s, like Fedco also offers so-called “day-neutral” varieties – varieties that straddle the demarcation line, as in “Candy” (adapted to 33 to 40 degrees latitude).

Of Copra seeds, Cipollini seedlings and Stuttgarter sets

In her early years of gardening, the Opinionated Gardener bought onion seeds and started them on the window sill two months before transplanting them into the garden. But there were problems with drying out, thinning, and the cat. So she moved onto sets, which are nothing more than tiny bulbs. But the choices were few: red or yellow or white and because they were grown one year and harvested while tiny to be planted as “sets” the next year, they often tended to bolt, “thinking” they were in the second year of their life cycle. The OG then turned to and has since stayed with “store bought” seedlings, which give her greater variety. And when she comes upon an unusual variety she would like to try she buys the seeds and asks other more patient gardeners to raise them for her.

Curious as to what some well known gardeners and farmers in the greater Farmington area grow and how they grow them, the OG called a few and learned that most swore by the F1 hybrid “Copra” because of its early maturity (104 days) and its long storage capacity. According to Johnny’s catalogue, this yellow “rock hard” storage onion grows best 38 to 55 degrees north latitude, making it a good Maine fit.

While Amy LeBlanc of White Hill Farm, Tomato Lovers Paradise and the Sandy River Farmers’ Market is a fan of “Copra,” this year she is also trying out two new varieties “Cipollini,” an open-pollinated, small, sweet, flat yellow Italian heirloom variety and “Dakota Tears,” an open-pollinated pungent variety that was 20 years in the making. Amy says she starts her seedlings in late February, planting 5 to 6 seeds per pot. She will set the seedlings out in mid to late May.

Dave Fuller of Cooperative Extension is also a fan of “Copra” but unlike LeBlanc he doesn’t start seedlings in the green house in late winter. Instead he plants his onion seeds directly into the garden on tax day, April 15th. He says he goes this route because it gets him into the garden early. He also says his garden-grown seedlings do well as they have no competition from weeds (a common problem with direct seeding onions). He plants the seeds an inch apart and then thins to three to six inches when they are about two inches tall. His other favorite is the day-neutral, slightly flattened large yellow F1 hybrid “Candy.”

Karla Bock of Hoof and Paw Farm and the Sandy River Farmers’ Market is also a fan of “Copra,” which she starts from seed in her New Sharon greenhouse in February. She also raises “Candy” (see above), “Walla Walla,” a mild white and short shelf life onion, “Red Wing,” a large, late onion that is said to be the “ultimate red storage onion and “Clear Dawn,” which was bred out of “Copra” and according to the Fedco Seed Catalogue is said to be the “best open-pollinated storage onion.” Unlike LeBlanc and Fuller, Bock also grows onions from sets, planting the standard for yellow storage onions – “Stuttgarter.” She gets her high quality sets from “The Maine Potato Lady”  which is located in Guilford. Check out www.maineppotatolady.com.

Two stories about onions

One of the favorite books in the OG’s library is Rebecca Rupp’s “Blue Corn and Square Tomatoes: Unusual facts about Common Garden Vegetables.” Published in 1987 by Storey Communication, Vermont, it informs us that “Onions were believed to have originated in Central Asia and have been domesticated since about 3000 BC. Moslem legend imprecisely dates them to the exit from the Garden of Eden: As Satan hastily departed, the angel with the flaming sword hot on his heels, onions are said to have sprung from his right footprint and garlic from his left.”

According to Indian legend, it’s n-propylthiol (the primary constituent in onion oil) that we have to thank for the Pleiades. A group of seven young Indian wives were fond of eating onions but their husbands, disliking the smell of onion breath became angry and forbade the practice. The wives, the story goes, after thinking it over decided they preferred their onions to their husbands, so they used magical ropes made of eagle down to float up to the sky, where they remain as the Pleiades, and presumably eating onions to their heart’s content.”