Harvesting, Curing, and Storing Onions

Storage onions are a variety of onions that will last in a cool location through the winter months. Learn which varieties to grow for food storage, plus tips on harvesting, curing, and storing onions for winter food storage.

I grow several varieties of onions each year including quick maturing scallions and other varieties fresh eating.

However, the majority of onions that I grow are storing onions meant to last through the winter months until the next growing season. Store onions add delicious flavor to winter soups, bone broths, chili, stews, and roasts.

How to Choose Onions to Grow for Food Storage

When choosing onions to grow for winter storing, select varieties that are known for their long-term storage capabilities.

Onions are also categorized as “short-day” onions or “long-day” onions. Long-day onions are what we grow in northern US plant hardiness Zones 6 and cooler. These are triggered to bulb when sunlight increases to 14-16 hours.

• See How to Grow Onions from Seed to learn more

Copra, Stuttgarter, and Redwing are my staple onions for long term storing over winter. These varieties work wonderfully for winter soups, chili, stews, and roasts.

Onions are the first seeds sown for the approaching growing season. The seeds are planted in January or February under grow lights, so they have plenty of time to grow before forming bulbs.

Onions can also be planted from transplants or onion sets purchased online or at your local garden center. Here in the north, onion seedlings or onion sets are planted in the garden in early spring, usually in April and grow all summer long.

Did you know that each hollow, green leaf represents a ring in the onion? Strong, healthy foliage growth before the bulbs form results in larger onions when mature and ready for harvesting.

When to Harvest Onions

Onions can be harvested at any time for fresh eating, but allow storing onions to mature fully to ensure the greatest storage capability.

Onions will let you know when they are finished growing. You will start to see the tops flop over. The onions will bend over at the stem and stop directing energy to the foliage.

There will be one or two plants at first. Eventually, the rest will follow. Depending on the variety, this usually happens in the first few weeks of August in my Maine garden.

Once the tops fall over, the onions are ready to harvest. Stop watering and wait for a dry period to dig up the bulbs.

How to Harvest Onions

Once you have determined that your onions are finished growing, it is time to harvest them. Choose an overcast day to reduce the sun damaging the bulbs as you work.

The easiest way to harvest a large amount of onions is to use a digging fork to carefully loosen the soil under the onions.

Once the soil is loose, grasp around the neck of the onion stalk and pull them up gently trying not to tear the roots, stalks, or bruise the bulbs because damage will reduce the onion’s storage life.

If the sky remains cloudy, I like to spread out the onions on my garden fence so any soil that is still clinging to the bulbs can dry and be shaken of before bringing the onions inside to cure. If the sun is out, spread the onions out in a dry, shady area out of direct sun.

Curing Onions

Curing onions allows the outer layers to dry out and tighten forming a protective wrapping around the bulb.

Onions cure best in a shaded, dry, and cool place. This can be in a shed or on a covered porch away from direct sunlight.

Spread the onions out or hang them so air can circulate around the bulbs and dry evenly. Our summers are humid, so I usually bring the onions inside and space them out on wire shelves in the basement where we run a dehumidifier to keep the moisture levels down.

Curing can take several weeks to a month depending on the humidity level. Onions are finished curing when their outer skins turn papery, the foliage at the neck constructs, and the foliage shrivels and turns brown.

Test one by cutting the stem about an inch from the bulb. The center of the cut area should not show any green. If it does, then the onions have not cured completely. Allow an additional week.

How to Store Onions

Once the onions are fully cured and all the foliage is dry and crispy, I like to take the bundles back outside for cleaning and trimming before storing.

Use scissors and cut the stems cleanly an inch or two from the bulbs and trim the roots. Brush the bulbs gently with your fingers to release any additional soil still clinging to the papery skin. Sometimes, the outer layer falls off. This is ok, but I try not to damage the skins any further than the first layer.

Inspect the trimmed onions are carefully. Any blemishes, bruising, or damage to the onions will affect their storage potential. Set these aside and use first.

Store cured onions loosely in baskets or hung in mesh bags in a cool, dark, and dry location for winter. Ideal storage temperatures are around 35-40˚F. Different onion varieties and storage conditions will affect how long they last.

Copra and Stuttgarter usually last the longest for me and usually begin to get soft or sprout around April. Check the onions every few weeks and remove any that develop soft areas or show signs of sprouting.

Trim off any bad areas and use the onion right away, freeze for later, or dehydrate into onion flakes and onion powder.

You May Also Like:

• 9 Crops to Grow for Food Storage
• How to Grow Onions from Seed
• Benefits of Crop Rotation in the Garden
• How to Make Chicken Stock from Scratch

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