Around here, we go through half a dozen onions a week because we’re slightly nuts, but they add so much flavor to meals, how could we not? There’s no possible way we could grow enough onions to provide for all year long unless we severely cut back, but who would want to do that? We do, however, try to grow as much as we can to meet at least some of our onion needs. There are several different types of onions: Bunching, walking, multiplier, and bulb are the most common. Here, I’ll be talking mostly about bulbing onions.
Once you figure out what works best for you, growing onions can be very rewarding. If taken care of in the beginning, they’re kind of a set-it-and-forget-it crop until harvest.
Growing onions can be very rewarding but it can also be a bit confusing. When you look up onions in your seed catalog, the description will read “Long Day,” “Short Day,” or “Day Neutral/Intermediate.” These descriptions refer to how and where, geographically, the onion grows best. When you plant onions, they’ll start out looking like scallions. When the day length reaches a certain point, the onion will start to bulb. The trick is to get the most greens on the plant before it does this. More and bigger greens = a bigger bulb. But you don’t want it to take so long that it will bolt too early before harvest and before you have a bulb.
- Short day varieties require 12 hours of daylight to start bulbing.
- Long day varieties require 14 to 16 hours of daylight to start bulbing.
The general rule is, if you live above the 35th parallel (draw a line from San Francisco to Washington, DC) you’ll want to grow long day onions because you will get longer days to encourage bulbing. Growing a short day variety in the north will cause your onion to bulb too early and end up being too small. Below the 35th parallel, you’ll want to stick with short day varieties. Growing a long day variety in the south will result in an onion that bolts before it ever bulbs because the days never got long enough. If you’re pretty close to the 35th parallel, you can do either type pretty successfully. Our most successful onion variety at our house is Yellow of Parma, which is a long day variety. Day neutral, also called intermediate, can be grown anywhere.
Next you’ll need to figure out what types of onions you want to grow. A good rule of thumb is the sweeter and milder the onion, the shorter the shelf life, or about two months. If you have a bumper crop of red onions, you can preserve them by pickling, or even caramelizing and then freezing them for future use. Onion varieties like Vidalia, Maui, most red types, and Grano are going to have a short shelf life and are best eaten fresh. The more pungent yellow and white onions, such as Yellow of Parma, Ailsa Craig, Copra, and Cortland, can be stored for as long as 12 months. We usually grow one-third red onions and one-third yellow onions.
There are several ways you can plant onions. You can use seeds, transplants, or sets. Sets are basically miniature onions that you plant out. Sets are 1-year-old onions, so they can sometimes be more prone to bolting early, as onions are biennials and flower in their second year. Onions transplant very well, so you can start with transplants to get a jump on the season. I usually start with seed but have found that onions are a bit finicky about direct sowing, so I start them indoors and then transplant them out. I like to use seed mostly because there are many more varieties available that way than in any other form.
You can plant your onions en masse. When you do, just tease them apart. I start them in flats in the greenhouse and once they are about 3 inches tall, I transplant them in a well-amended, loose bed of soil. Don’t use a high nitrogen fertilizer for onions, although you do want to offer them some nitrogen. What you want is more phosphorus to encourage root growth. A good amendment would be a combination of poultry and steer (or goat) manures.
There are two very important things to know about growing onions. They need a good amount of water, especially when they’re young, and they really dislike competition from weeds. You can mulch around them with straw after they’re big enough to help with both of these issues.
Harvesting Onions, Curing Onions & Storing Onions
When the tops of the onions start to fall over, you are nearing harvest time. We usually wait until almost all of the tops are down and most are beginning to dry up before harvesting. We harvest in August, when it’s bone dry here, but if you live somewhere that rains, make sure to wait until you have a nice break in the rain and the ground has a chance to dry out some before harvesting. Don’t pull the onions out by their tops. Instead, use a shovel or a fork to gently lift them out of the ground. You want to keep the top on through the curing process to avoid opening the onion up to pathogens that could cause their early demise.
Other things to watch out for are bruising and onions that have bolted. The bolted onions will have a stiff stem coming up through the center. It is safe to assume that any onions that have dropped on the ground are bruised. These we set aside to be used first. The rest of the onions we lay out on a table in a single layer in a warm area with good circulation but out of direct sun. We have a metal patio table with a mesh top that works well for this but we also use a wood table with just as much luck. Don’t wash them or peel off any layers.
Allow your onions to cure for about 2 weeks. The tops and roots of the plant will dry down to nothing. Once they are completely dry, the curing process is done and you can trim the top and the roots. Store them in a cool, dark place. We store them in small burlap bags in our water tower and garage. I prefer the smaller bags because it allows all of the onions to get plenty of air circulation. The larger, coffee-bean-sized burlap bags always end up causing the onions in the center to rot first.
A proper curing will ensure that your onions keep for a good, long time. I do find as they age they become more pungent and oh, boy, can they leave you in tears! Just throw them in the freezer for about 10 minutes prior to cutting to avoid crying all over your cutting board.
Some resources for onion seed:
Rachel’s friends in college used to call her a Renaissance woman. She was always doing something crafty, creative, or utilitarian. She still is. Instead of crafts, her focus these days has been farming as much of her urban quarter-acre as humanly possible. Along with her husband, she runs Dog Island Farm, in the San Francisco Bay Area. They raise chickens, goats, rabbits, dogs, cats, and a kid. They’re always keeping busy. If Rachel isn’t out in the yard, she’s in the kitchen making something from scratch. Homemade always tastes better!