Here we are, a whole season after the first onion seeds were sown, and those little specks have slowly grown into a bed of bulging, fragrant alliums.
While onions can be harvested and eaten at any stage, the most satisfying part of growing onions is being able to pluck a fresh onion from the pantry months after you’ve plucked it from the ground. Curing makes that happen.
Curing is a month-long process of drying down your onions to prep them for storage. Once properly cured, onions store for a very long time — through the fall and winter, and sometimes even spring under the right conditions. (Though I’ve never actually had an onion store through the spring, since my harvest is long gone by March. What can I say, I love onions.)
When your onions are vigorously growing through the longer days of spring and summer, their stems are lush and happy and green. You might even have a few onion blossoms topping those stems (more on those later).
When they’ve finished developing, you’ll notice the lowest leaves start to yellow and wither. Shortly after, the stems will flop over at the neck, as if all your plants had just died. The onions won’t look very appetizing either. Fear not. Wait for most of your crop to flop, then bend over the stems of any remaining upright plants. You can simply bend them above the bulb; this will signal the plants to enter dormancy.
If some of your onions have sent up flower stalks, you can just leave them be. The leaves around the stalk will still wither naturally when the onion is ready for harvest, so you don’t have to bend over the stalk. I don’t recommend cutting it off, because it could introduce bacteria into the onion during the curing process.
At this point, stop watering and leave the onions in the ground for 7 to 14 days (depending on how dry or humid your climate is) to allow them to fully mature.
On a dry, sunny day, carefully pull each onion out by the bulb, or by digging around it. Grasping the weakened stem could cause it to pull off entirely, and you want the stem intact to reduce the likelihood of rot. Lay the onions out on the ground, or in another open, sunny area, for a day or two to dry out the roots.
But wait! You’re not done yet. After a nice day of getting their tan on, move the onions into a breezy, shady spot (such as a covered porch, or under a tree) and lay them out one by one. You don’t need to clean off the onions yet. Just set them out to dry, dirt and all, until the stems turn brown and brittle. This rest period allows the onions to go deeper into dormancy so that they’re less susceptible to disease.
If you have absolutely no shade around your house, you can lay them in the sun but covered with a thin cotton sheet (never plastic or canvas, which could stifle them) to prevent sunburn. If you tend to get rain in the summer, you can cure your onions in a garage or basement, but turn them over a couple times a week to ensure even drying. The important part of curing is having plenty of air circulation around the bulbs. Because of this, it’s best to lay them out without crowding them, rather than heaping all your onions into a basket.
This last step of the curing process takes two to three weeks. You want your onions dry, dry, dry. The roots will become wiry and the papery outer skins will tighten around the bulbs.
Now you can clean ‘em up by trimming off the roots and stems with shears. A couple layers of the outside skin will usually flake off with the stems, leaving you with a smooth, spotless onion.
If you had a few onions with flower stalks growing through the bulbs, use those up first. The stalks retain a lot of moisture (even after curing) and will cause the onions to decay sooner in storage. They’re perfectly fine to eat and usually keep for a month or two.
For the rest of your onions, stash them in a cool and dry, dark and airy space, inside brown paper bags, mesh bags, milk crates, wire or wooden racks, or any well-ventilated storage shelf. Sweet, juicy onions (including many short-day onions) tend to not store as well as firmer, long-day varieties, so you’ll want to use them first.
Keep in mind that even after curing, onions are still very much alive and need cool, dry conditions to stay dormant. Any change in temperature or humidity can cause them to break dormancy and sprout again. You should check your onions every few weeks for green shoots that might emerge in storage. (I once let them linger in a warm room for a couple of months, and came back to alien-like tentacles taking over my shelf. The onions were still good to eat, though.)
If you happen to have some teeny tiny onions (I usually get a few that never got around to growing, but are too small to be used like shallots), cure them and save them for next year — you’ve just grown your very own “set” of onions! Replant them in the spring, where they’ll mature into full-sized bulbs in less time… and you’ll have a new harvest even sooner!