It’s almost time to start thinking about planting onions. Around here we go through half a dozen onions a week because we’re slightly nuts, but they just add so much flavor to meals, how could we not? There’s no possible way we could grow enough onions to provide us all year long unless we severely cut back, but who would ever want to do that? We do, however, try to grow as much as we can so at least some of our onion needs are met. There are several different types of onions – bunching, walking, multiplier and bulb onions are the most common. I will 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 the are 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 at a seed catalog you will come across in the description of the onion as being “Long Day,” “Short Day,” or “Day Neutral/Intermediate.” These descriptions are about how the onion grows and where, geographically, it is best grown. When you plant onions, they will 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 = 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 14-16 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 will 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 will 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 both types pretty successfully. Our most successful onion variety at our house is Yellow of Parma which is a Long Day variety. Day Neutral, also sometimes called Intermediate, can be grown anywhere.
Next you will 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 – about 2 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 1/3 red onions and 2/3 yellow onions.
There are several ways you can plant onions. You can use seed, transplants or sets. Sets are basically miniature onions that you plant out. Sets are one year old onions so they can sometimes be more prone to bolting early since onions are biennials (they flower 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 will start them indoors and then transplant them out. I like to use seed mostly because there are many more varieties available in seed than in any other form.
I prefer to start my onion seeds at the first of the year. Planting them in the fall, I find, throws them out of whack when the days get shorter and then get longer. When this happens the plants think they are heading into their second year so they bolt almost immediately in the spring. You can plant them en masse and when you plant out just tease them apart. I start them in flats in the greenhouse and once they are about 3″ tall I will transplant them in their well amended, loose bed. Don’t use a high nitrogen fertilizer for onions, though 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 about growing onions. They need a good amount of water, especially when they are young, and they really dislike competition from weeds. You can mulch around them with straw after they are big enough to help with both of these issues.
Harvesting, Curing and Storing Onions
When the tops of the onions start to fall over you are close to harvest time. We usually wait until almost all of the tops are down and most are beginning to dry up before we harvest. 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 fork to gently lift them out of the ground. You want to keep the top on through the curing process so you don’t open up the onion to pathogens that could cause their early demise.
Other things to watch out for are any 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 ones 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 as well 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 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 will 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 help avoid crying all over your cutting board.
Some good onion seed resources: