When Do You Harvest Onions? Here’s What to Look For

Onions can be harvested at any point in their growth, but to maximize storage life, it’s important to follow some key guidelines. When you’re ready to gather your homegrown onions, knowing when to harvest and how to properly cure and store them will allow you to enjoy the harvest well beyond the gardening season. This guide will help you understand these important steps.

When Should Onions Be Harvested?

Onions should be harvested in dry weather because wet soil and humid conditions increase the risk of spreading diseases. The more you let the onions mature, i.e., the more dry matter they contain, the sharper they taste and the better they store.

There are two indicators that onions are getting ready to harvest:

• Dried, fallen tops: Once an onion’s top has dried and fallen over (the recommendations on which percentage of the foliage should have dried and toppled over vary, ranging from at least 50% to 80%), it can be harvested.
• Dry necks: When the neck (base of the stem right above the bulb) has turned from green and fleshy to dry, the onion is ready to be harvested. You can also roll the neck of the onion between your fingers. The onions are ready to harvest if the necks feel tight and the layers don’t slide.

How to Harvest Onions

When harvesting onions, it is key to be extremely careful because they are easily bruised, which makes them prone to rot during storage. There is no single way to harvest onions. Ideally, do not use a sharp instrument. If the soil is soft and loose, pull them out by their foliage. Otherwise, use a garden fork to loosen up the soil around the bulbs, taking care not to damage them, and then pull them out by their tops.

Gently shake the bulbs to shake off access soil or remove it with a gardening glove or a soft brush.

Curing and Topping Onions

To cure onions promptly after the harvest, they need to be cured at a temperature between 75°F and 90°F for two to four weeks.1 To prevent them from getting wet in rainfall and to protect them from insects, it is best to cure them indoors in a well-ventilated place.

At the end of curing, the outer skins and the neck should be dry and papery, and the neck should be tight. Any moisture and openings in the neck will make the onion prone to rotting in storage. Curing also improves the colors of the scales (they look like thick outer skin, but they are modified leaves that protect the onion from water loss).

After curing is complete, cut the neck to 1 inch above the bulb. This is called topping the onions, and it can be done with clippers or pruners.

Storing Onions

Sort out defective onions before storing—any that have sprouted, have disease or insect damage, green spots, bruises, or an extremely thick neck. They can be perfectly edible, but they are not suitable for storage and should be used as soon as possible. Defective onions release moisture, which encourages disease in all the stored onions.

• Store the onions in single layers in a produce mesh tray, an old window screen, or screen door, or anything else that allows good air circulation.
• Store onions at a cool temperature, between 32°F to 36°F, and at a relative humidity of around 65%. Bring them down to that temperature slowly by leaving them in a barn or garage in the late summer and fall when the temperatures drop gradually.
• The final storage temperature should be above freezing but below 40°F. Any temperature above that will make the onions sprout.

Saving Onion Seeds

Because onions are a biennial crop that will only flower and set seed in the second year, you won’t be able to collect seeds from any onions that you started from seed the same year. But if you use onion sets, which are onion bulbs in their second, final year of growth, you can let some of them go to flower to collect the seeds.

• After the plants have finished blooming, they will form seed heads. Let those dry on the plant, but make sure to collect them before they open and scatter.
• Gather them in a paper bag. Close the bag and shake it to dislodge the seeds.
• Pour the contents of the bag on a tray or a large plate. Separate the seeds and discard the rest.
• Let the seeds air-dry for a few days in a warm location indoors away from direct sunlight.
• Store the seeds in a paper bag in a cool, dry place. Onion seeds remain viable for two years.