When and How to Harvest, Cure, and Store Onions: Step-by-Step Guide

You’ve grown your best crop of onions, and it’s harvest time. You can’t eat 20 or more onions this week, but you want to store them to use later. That’s where curing comes in. 

Curing onions dries the outer layers and seals the neck of the bulb, helping prevent rot during storage. With proper curing and storage, many onion varieties can last for several months.

We’ll show you how we harvest, cure, and store our heirloom onions, so they’re fresh and tasty for meals months later.

You can harvest and eat onions at any stage. However, if you want onions that you can store for several months, you need to properly cure them first.

Curing onions is the process of drying the outer layers of the bulb and the neck (the area where the leaves meet the bulb). This reduces moisture, helps prevent rot, and prepares onions for long-term storage.

When dried, cured, and properly stored, onions can keep for months instead of just weeks.

Onions are ready to harvest when the green leaves start to turn brown, and the tops fall over. At this point, they’re no longer actively growing and won’t get any bigger. You can stop watering to get them ready for harvesting. 

Ideally, you want to stop watering onions 1 week before harvest. This will help the onions start drying out on those outer layers. 

Manually knocking them over doesn’t seem to help as much as letting them stop growing naturally.

Once they are ready to harvest and you’ve stopped watering for 1 week, you can dig them out. If they’re mostly on top of the ground, onions are easy to pull. But don’t yank them by the leaves. You want the leaves to stay attached for the curing process. As the onion cures, the neck will naturally close up and dry. A closed, dry neck allows the onion to store well without rotting prematurely.

You can loosen the soil with a digging fork or shovel. Be careful not to cut or damage the onion. Shake off the dirt, but don’t worry about getting it off. You can leave the dirt on for now.

Don’t wash them. Don’t add any moisture to your onions.

• Most tops have fallen over naturally.

• Leaves are turning yellow or brown.

• New leaf growth has stopped.

Note about harvesting and rain: If rain is in the forecast and it’s time to harvest, you may need to pull them and take them inside. Too much water can affect how well they cure. 

Once you’ve pulled the onion, you can let it stay out in the sun for a day if it’s not too hot. 

For areas with high heat and humidity, you don’t want to leave onions in the ground for more than 2 weeks after the leaves fall over. They may start to rot.

The curing process for onions is very simple. The most important thing about curing is warm, dry airflow.

If it is a dry day and the soil is dry, you can let the onions stay on the ground in the sunshine. After a day in the sun, you can continue to let them cure away from the sun. You will want to put them in a place away from critters, too. 

We bring our onions indoors and place them on wire racks. We also use a fan to ensure good airflow. It does make for a strong onion smell if you have a lot of them. You want to give them enough space for good airflow.

We don’t worry about cutting off the tops at this point. The leaves will continue to dry. 

• Good air circulation

• Temperature: 75 to 80ºF

• Low Humidity

• Protection from rain

• Out of direct sunlight after initial drying

When is an onion “cured” and ready for longer-term storage? It will take 2 to 4 weeks for an onion to cure. It is considered cured when the outer skin is dry and crinkly. The roots will also be dry and brittle. 

Cured Onions:

• The neck feels dry and tight.

• The outer skin is papery.

• The roots are dry and brittle.

• No green tissue remains near the neck.

If any part of the neck still feels soft or moist, continue curing for a few more days.

• Washing onions before curing

• Storing onions before they are fully dry

• Piling onions on top of one another

• Curing onions in a damp garage or basement

• Storing onions in plastic bags

Once your onions are sufficiently dry and cured, they can be stored for several months. You can cut off the tops about one or two inches above the bulb. You want to leave some of the neck because it has formed a dry barrier. You can also trim off the roots and brush off extra dirt. 

Some people braid onions to hang them in storage. Hanging in mesh bags works too. Just ensure the onions are thoroughly dry so they don’t grow mold.

Place onions in mesh bags to hang in a cool, dry location. Wire baskets or crates that have airflow are also good storage options.

• Cool, dry, dark, plenty of airflow

• Ideal temperature for onion storage - 32 to 40ºF (warmer temperatures can lead to sprouting, so store in a dark location)

• Humidity - 50 to 70% (too dry, they shrivel faster, too moist, they can rot)

• Don’t put onions in plastic bags or store them near potatoes.

Check them every few weeks and discard any that have mold. This can spread to other onions.

Variety determines how long an onion can be stored. Sweeter varieties don’t store as long as the more pungent ones. Sweet onions generally last 1 to 3 months, while strong, pungent onions typically last 6 months, and some can last 10 months.

We don't have a perfectly controlled onion storage room, so we work with what we have and check them frequently.

Onions with a thick neck won’t store as long as those with a small neck. Use those ones first.

Curing onions is a simple but important step if you want to store your harvest for more than a few weeks. By harvesting at the right time, allowing the bulbs to dry completely, and storing them in cool, dry conditions, you can enjoy homegrown onions for months after harvest.

With good airflow, low humidity, and a little patience, your onion harvest can stay fresh and flavorful well into the winter.