Guide to Harvesting, Curing and Storing Onions

Onions are a highly generous mainstay of the home vegetable garden. In a good year, you’ll harvest many more than you can use immediately. But one of the great advantages is onions can be stored for months while remaining in perfect condition.

By following a simple method for harvesting and preparation, you can enjoy your homegrown onions right through until the next growing season arrives. Here’s what to do.

Growing onion plants produce lush, green leaves and stems, often topped by the distinctive spiky flowers. But by mid to late summer, the plants will begin to wither and turn yellow, starting at the base of the leaves and moving upward. Although this can be worrying for beginner onion growers, it’s a natural stage in the life cycle, and it’s not quite time to harvest yet.

Wait a little while, and the plants will begin to flop over sideways, with the stems bending just above the crown of the bulb. Once this begins to happen, stop watering the onion patch to reduce the risks of rot after harvesting.

Once at least half the plants have flopped over in this way, gently bend the remaining upright stems to match the others. This signals to the plants that it’s time to go into dormancy for the colder winter months.

The onions are ready to pick. Wait for a dry sunny day and then pull all the plants up gently by the bulbs, first clearing away a little soil if necessary. Avoid pulling them by the stem, as any damage to the plants’ upper parts increases the chances of rotting in storage, and can also introduce disease or fungus. Leave the uprooted onions lying in an open, dry, sunny area for a day or two so that the roots can start to dry.

At this point, the onions are ready to eat. But if you plan to store them for later use, an extra stage known as curing is needed to prevent mold, rot or the sprouting of new green shoots.

Curing starts by laying out the whole, uncleaned onions in a dry, sheltered and shady place, in a single layer with as little touching as possible. A covered porch or well-ventilated garage is an ideal curing space. You can also lay the onions out in the open covered by a thin, breathable sheet to protect them from direct sun.

Keep the onions well ventilated, either through natural breezes in the open air or if they’re indoors by turning them over every few days to dry each side evenly.

After between two and four weeks, the stems should be fully dry, brittle, and brown, while the skins should be papery and shrunken to make a smooth, tight bulb. At this stage, you can trim off the roots and stems using a sharp pair of scissors. Often, the top layer of skin will also fall away when you do this, leaving you with a clean bulb that’s ready for storage.

The stronger and more pungent the onion the variety, the longer it will store. The sulfurous compounds that cause the eye-watering smell also act as a preservative. But whether you have strong or mild varieties, keep them in a cool, dark, ventilated space, in paper bags, mesh sacks or baskets covered with a sheet of brown paper.

With dry conditions and a consistent temperature of 40-50°F (5-10°C) the bulbs will stay in their dormant state for between three and twelve months, depending on variety. Check the stored onions every couple of weeks or so. Remove any which are sprouting green shoots. Sprouting onions are still fine to eat, but discard any which are turning mushy or giving off a bad smell.

Ready to learn more about storing your homegrown vegetables? Check out our handy guide to successful vegetable storage, and enjoy the fruits of your harvest deep into winter.