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If You’re Thinking About Growing Onions From Seed, It’s Time to Get Started

There are some things I never forget: Where each plant in my garden came from. Who unlocked the secret of successfully growing carrots for me (John Navazio, then a senior scientist at Organic Seed Alliance). Who shared the best strategy for keeping tomato diseases at bay (Tom Stearns, the founder of High Mowing Organic Seeds).

And who helped me understand the finer points of growing onions from seed: Don Tipping, the founder of Siskiyou Seeds, an organic, farm-based seed company in Oregon.

Mr. Tipping, who started the company in 1997, likewise recalls the provenance of each piece of tactical wisdom he inherited from others, offering a grateful nod to mentors along with his instruction. His onion teachings include insights from two well-known organic farmers, one from either coast, and aphorisms from older traditions.

“The best fertilizer is the gardener’s own shadow,” he said, repeating a Chinese proverb that isn’t onion-specific, but advises us to be observant. Rather than getting swept up in a flurry of chores, it counsels us to mindfully read the signals about what each particular crop needs.

It was by chance, about a decade ago, that Mr. Tipping and I got to talking onions, or Allium cepa. We might instead have discussed any of the other open-pollinated vegetables, flowers and herbs (culinary and medicinal) that he was working with — breeding projects that have yielded vividly colorful flour corn, like Oregon Blue and Siskiyou Pink, and a super-hardy Scotch curled kale known as Alive Vates.

Lately, he’s been busy nudging cactus-type zinnias to fanciful extremes — among them, a fantastically frizzled fuchsia selection called Crazy Legs and others that approximate the look of undersea anemones (his Tidepool Mix).

Siskiyou, a family-run operation at an elevation of 2,000 feet in the Siskiyou Mountains of southwest Oregon, near the California border, has close to 1,000 varieties in its collection, about 700 available in any given year. There are other offerings, as well: For 26 years, Mr. Tipping has provided training for organic gardeners and farmers, and he is an enthusiastic creator of a long-running blog and how-to videos on YouTube.

“From the outside, our job may seem like we’re just selling seeds,” he said. “But really what we’re doing is providing a service: We’re facilitating the experience of gardening.”

When we first met, Mr. Tipping had been tinkering for more than a dozen years with Walla Walla Sweet Onion, among the best-known Northern-adapted sweet Spanish varieties. His enthusiasm about the progress he had made, resulting in a selection he called Siskiyou Sweet, sparked our initial conversation — and my interest in trying to grow onions from seed.

Since then, I haven’t bought mail-order onion seedlings (those $15 or $20 bundles of 50 transplants). Instead, for maybe $5 a packet of 100 or so seeds, I can choose from a much wider range of sizes, shapes, colors and flavors than I would be able to if I were buying transplants (or onion sets, those small bulbs that are the other possible starting point).

In addition to a basic yellow workhorse like Newburg, you might try a strong-flavored red like Rossa di Milano and some choice little flattened, round Cipollini types like Borettana, an Italian heirloom dating to the 1400s, or the torpedo-shaped red Cipolla di Tropea. Be sure to grow one specifically rated for long storage, too — perhaps Front Range Yellow Globe — to keep you in homegrown onions for months.

Also important: Choose an onion matched to your region or, specifically, your latitude.

Onions are categorized according to the hours of daylight each variety requires to initiate bulb formation. In the South, where onions are typically sown in the fall and transplanted to harvest in late spring, short-day varieties are the choice; in the Northeast, where bulb formation happens in the summer from spring transplants, long-day varieties are indicated. Intermediate-day types suit the middle latitudes.

Onions are one of the first crops sown during indoor seed-starting season in the Northeast — around early February — and are ready for transplant eight to 10 weeks later. At Siskiyou, seedlings get their start in a greenhouse; home gardeners can grow theirs under lights.

Giant onions are not Mr. Tipping’s end game. And cell packs — those commonly used seed-starting trays with individual compartments — are not his starting point.

Instead, he sows seeds into open flats — shallow boxes without compartments — for less restricted root growth, which pays off especially when early spring weather is unsettled and the seedlings must wait a couple of extra weeks before being liberated into the open ground.

“They’d suffer if they had to be held back like that in cells,” he said.

His flats are homemade, of wood, but commercial plastic ones with drainage holes will do, with a tray to catch water underneath.

Mr. Tipping fills each flat with a homemade potting mix of about 10 parts well-aged compost to one part sand, which improves the drainage and helps limit surface algae growth and damping-off disease. To every wheelbarrow load, he adds about a quart of crushed eggshells (for calcium) and a similar amount of seaweed powder (for trace elements).

After filling the flats, he uses his finger or a piece of wood to make four or five parallel furrows lengthwise across the surface. Into those furrows he sows eight or 10 seeds an inch, covering them with about a quarter-inch of the potting mix.

Each flat sown that way may yield several hundred transplants of a single onion. Gardeners who don’t need that many can modify the layout: Perhaps make just two or three rows, one for each variety, or make shorter furrows across the width of the tray, one for each type of onion. Because most of us are handling far less seed than someone planting on a farm scale, we can take our time and sow less thickly.

“If you are able to space them out to about four seeds per inch,” Mr. Tipping said, “then you can really get pencil-diameter transplants.” You rarely get more than a few such robust seedlings in mail-order bundles.

The seedlings’ eventual destination is a sunny location in well-drained, fertile soil.

“We spread a half-inch to an inch dressing of compost on all the onion beds,” Mr. Tipping said. “Because they’re an inefficient feeder, they need the fertility right there to achieve good size.” (If you like, he said, you can substitute organic fertilizer for compost; apply at the recommended rate on the package.)

At transplant time, another decision affecting bulb size comes into play.

Some varieties Mr. Tipping grows, like the heirloom Ailsa Craig and his Siskiyou Sweet, can get as large as a pound each — or sometimes more than two pounds. But “who wants, or needs, a two-pound onion, or even a pound?” he said. “We aim for half-pound bulbs.”

A tactic he learned from Eliot Coleman, the influential Maine-based organic farmer and author, steers the seedlings in that direction. Instead of planting each one individually, he scoops up a few at a time from the flat and plants them “in little clusters, two or three to a hole.”

Depth-wise, “just get the white part underground — that’s a good indicator mark,” he said, referring to the spot where the roots and bulb-to-be meet the green of the leaves.

Mr. Tipping starts leeks (Allium porrum) in open flats, too. But they take longer to reach the transplant stage than onions, perhaps 10 to 12 weeks. With leeks, he avoids cluster planting. At transplant time, he makes six-inch-deep furrows, like small trenches, spacing an individual seedling every 10 or 12 inches within them.

“We plant them at the bottom of the furrow, leaving the ridges to hill the plants up at the first weeding time,” he said. That hilling up promotes leeks with longer white shanks. Older varieties, like Ester Cook and Falltime, are among Mr. Tipping’s favorites.

At the farm, he leaves a foot between rows of Allium to allow for easy weeding with the six-inch blade of a stirrup hoe. In the backyard, where you’re more likely to be hand weeding, each onion cluster could be planted on an eight- or 10-inch grid in each direction.

Weeding, Mr. Tipping noted, is something onions will require. At Siskiyou, they are weeded three times a season. Just look at their structure, he said: Unlike, say, a lettuce seedling, which forms a rosette of leaves that shade and basically mulch the ground around the plant, vertical onions have no such built-in way to outcompete weeds.

“You can grow weeds or you can grow onions, but you can’t grow both,” he said, crediting Warren Weber, considered the godfather of organic farming in California, with the critical reminder that it will be up to the gardener or farmer to give the onions the advantage they require.

One more tip: Think about “harvesting sequentially,” Mr. Tipping said. Don’t wait to enjoy your onions until all of the bulbs have reached full size and the tops have begun to yellow and fall over, signaling readiness — especially if you’re growing the sweet Spanish types.

Try harvesting some when the tops are still green, for so-called spring onions, whose immature bulbs tend to be more delicate in flavor. The tops make a great substitute for scallions. Or maybe make onion-leaf pesto, he suggested.

Either way, you can claim credit for the main ingredient, from seed to table.

Margaret Roach is the creator of the website and podcast A Way to Garden, and a book of the same name.

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