Growing Onions the Easy Way

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A sprouted onion rests in a clay pot.
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Onions drying after harvest.
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Sowing red onion sets might be a way to get your onion crop off to a quick start.
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A bumblebee finds an onion blossom irresistible.
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A small-market farmer grows onions to be sold in farmers’ markets.
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Baskets of onions are on display at a local farmers' market.
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After onions are pulled from the ground, they are left in the field to dry and cure before storing.
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Yummy green onions, just pulled from the garden, await the cook’s pleasure.
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Gritty cries as he chops an onion.

“It’s hard to imagine a civilization without onions.” — Julia Child

Indeed it is … and apparently, from their cultivation throughout at least 5,000 years of history, it has been hard for a civilization to imagine itself without the onion as well. Even as much as I fall into the camp of onion lovers, I can’t help but find it somehow odd that a root, even one able to garner such passion both in its enjoyment and its dislike, has become so instrumental in our evolution as gardeners and cooks. Still, every year, new lovers of the onion in its variant forms are born, and, every year, new gardeners try their hand at growing onions for the first time while seasoned growers work to improve their harvests.

The common onion (Allium cepa) is found and loved in many forms around the world. The yellow, white and purple (or red) onions; Welsh bunching onions; “walking” onions; and, of course, the scallion (or green onion) are probably the most popular, and many localities have their own favorites. Take, for instance, the “ramp” (wild onion/leek) of the Appalachian region whose fans hold festivals in honor of the vegetable’s arrival every spring.

Besides their pungent, sometimes sweet and always distinct flavor, onions have become popular for many of their other qualities as well. They are relatively easy to grow, whether from seed or starts; they are tolerant of a variety of soils; and they are transportable. On top of that, they can keep for a long time.

Why onions?

Once you’ve decided to add onions to your garden, the first thing to do is to figure out what you want to use them for — whether it be fresh summer salsas, green onions to top your favorite chili, storage onions to cook with all winter, or all of the above.

Choosing a variety can be a big decision if you have only a small garden, and it can be overwhelming if you have so much space you want to try them all. There are some easy ways to help narrow the search.

First consider where you are in relation to the sun. Many types of onion are dependent on the number of hours of sun a plant will get during the day to trigger the bulbing action itself. Typically these are referred to as “long-day” or “short-day” onions. Because onions are a cool-season crop, they grow best in the early or late season’s cool weather and have a long growing period before they’re harvested.

Areas in the northern parts of the country do better with long-day onion varieties that can be planted in the early spring and grow through the longer summer days. If you’re in the southern part of the country, where the cool weather needed for good growth is found during the shorter winter days, then you’ll want to choose a short-day variety and plant in the fall.

Long-day varieties you might be familiar with are Red Cipollini, Yellow Sweet Spanish, Southport White Globe or Walla Walla. Some popular short-day length types are Red Burgundy, Yellow Granex, Vidalia or White Granex.

The good news is that while the different onion varieties may need differing day lengths to bulb, they all can be harvested young as green onions.

Growing onions: where to start

Now might seem like the right time to talk about prepping your soil and how to plant — and in a way it is. The process depends on where you want to start, indoors or out, and how you want to start, seeds or starts. Because I’m in the northern part of Utah, and our winters are not hospitable for getting an early start on seeds outdoors, I like to start either from seeds indoors or with a small bulb start called a “set” early in the spring.

Sets are an easy way to get started. You simply prepare the soil, plant the small bulb, fertilize occasionally, water and wait. I’ve grown many harvests this way, and the method works great.

A few notes: Counter to what you might expect, the larger sets do not produce larger bulbs. Larger bulbs already have more energy stored, which makes them more likely to bolt and set seed before they have a chance to develop, so look for planting sets about the size of a marble. Also, plant the sets at the final spacing you want the onions in, approximately 3 to 4 inches apart, depending on the variety. You can plant sets in the ground in the North as early as mid-April, while in the Southern states you will want to plant your short-day varieties in October to grow through your mild winter.

If, on the other hand, you decide you want to start your onions from seed, it’s about as easy as it comes. Around January, or August in the southern parts of the country, start with a good soilless potting mix, sprinkle your seeds evenly in either a single large pot or a starter tray filled with mix, cover with about a quarter inch of the mix, and water in. You can use individual cell packs if you’d like, but the seedlings are going to be trimmed, thinned and transplanted before all is said and done, so you don’t really need to.

Place a plastic top or a loose layer of plastic wrap over the seed tray, and after a week to 10 days, you’ll begin seeing seedlings pop up. After they’ve emerged, keep them in a cool and well-lit area or under artificial lighting and feed at least once per week with a water soluble fertilizer.

Once the starts have grown to a wispy 3 or 4 inches tall, you’ll want to thin them out to about 1/4 to 1/2 inch apart and clip the tops off so they’re only about an inch tall. This is your first harvest. Feel free to snip these tasty little bits over a baked potato or salad.

Trimming starts like this helps the plant use its energy for growing roots and building a thicker bulb at the base, both of which will help the onion survive transplanting. Continue fertilizing and trimming the onion starts until a couple of weeks before you plan to transplant them in the garden, at which time you’ll let them grow just as they will.

Prep the garden

Now that we have our starts grown, have selected our sets, or sown seed, it’s time to prep the garden beds and get planting.

As I mentioned before, onions are tolerant of a variety of soil types as long as the soil is rich, well-drained and moist. Onions are heavy feeders, so a rich soil is a must. As for well-drained and moist at the same time, think of a wrung-out sponge. There’s water available, but it’s not really soaked. That’s kind of the way an onion likes it. Although their large cells are made up mostly of water, onions are susceptible to rot if kept too wet. On the other hand, they do still need consistent moisture levels in order to produce those large bulbs.

The best cure I know for all of these requirements is a healthy dose of good organic compost turned into the soil before planting. Because compost is a great soil conditioner and helps increase the moisture retention of the soil while also allowing large amounts of slow-release nutrients to add fertility to the soil, it is the perfect soil amendment before planting onions.

In addition to well-composted organic matter, it is recommended to add 1 to 2 pounds of all-purpose fertilizer per 100 square feet of soil at planting time. Turn all of this into the soil to a depth of 6 to 8 inches.

To help provide a well-drained soil, onions do best when planted in raised beds. This doesn’t mean building boxes to plant them in, just that the soil should be mounded up approximately 4 inches into beds at least 20 inches wide. Keep the bulbs higher than the drainage area and water around them so they can pull water up as they need it without sitting in it and causing rot.

Now you can lay out a rough spacing to give yourself a good idea of how many starts you can fit per bed in double rows about 10 inches apart. Set bulbs should be planted just deep enough so the tops of the bulbs are barely visible at the soil level. Seedling starts should be planted so about two-thirds of the plant is above the ground.

If you’re direct seeding, you can drag a shallow furrow and sprinkle seed in just a quarter-inch below ground and sweep the soil over. You’ll need to thin the seedlings later, but again these are just green onions and can be a great second harvest.

Mulching around the onions is great for weed control and moisture consistency, but I’ve found that with seedling starts, or when starting from seed, this is best done when the plant has become established. There’s less chance of causing damage to the tender plants, and it tends to deter some of the small insects that live in the mulch cover from causing damage to the young plants.

Easy care

Throughout the growing season, onions require little care other than regular watering — deep enough to soak the ground and just often enough to allow it to drain away in between — and weeding. Onions do not compete well with weeds and will benefit greatly from regular weeding.

Once per month, it is recommended to side dress with a nitrogen fertilizer (1/2 pound per 100 square feet) until the onions have set bulbs. Do not fertilize during the last month or so before harvest. This can cause late-season growth and decrease shelf life of the cured onions.

You’ll know your onions are ready to harvest when the tops have dried and fallen over. It’s best to gently pull them from the ground and let them lay on the soil for a couple of days to dry and finish curing if the weather permits. After the outside paper skins have completely dried, they can be braided, or the tops can be cut 1 to 2 inches above the bulb, and the onions placed in a mesh bag.

Store onions in a dark, cool place away from other vegetables, and enjoy them for as long as you can. Remember when grabbing one for dinner to check for mold or rot on any of the other onions in the bunch and discard immediately for the longest shelf life.

Whether you love them or just like a little taste here and there, onions are a king in the kitchen and have held a place in our gardens for thousands of years. With a little effort and by following some simple steps, you can plant, harvest and enjoy onions in your own garden as well.  

GRIT Blogger Paul Gardener and his family enjoy the fruits of their labor throughout the year at their suburban Utah home.

Read more: Learning how to grow onions also involves learning to cook with Vidalia onions. Try these tasty onion recipes in Vidalia Onion Committee Offers Recipes.

Published on Sep 27, 2012

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