Last Updated on October 8, 2026

How to Harvest, Cure and Store Onions

Pull storage onions when about half the tops have fallen over, cure them for 2 to 3 weeks in a warm, dry, airy spot out of the sun until the necks are tight and the outer skins rustle, then store them at 32-40°F and 65-70% humidity in a mesh bag, crate or braid. The harvest sign comes from University of Minnesota Extension, and the curing and storage numbers from Iowa State University Extension. Sweet onions are the exception: they keep for weeks to a few months, not the whole winter.

Growing them is in my guide to growing large onions. This page starts when the tops fall.

Onion harvest, curing and storage at a glance

Each step, with its source, is below.

When to harvest onions

Go by the plants, not the calendar.

• The tops fall over. Pull when about half the tops are down and dry (University of Minnesota). For onions you want to keep all winter, the UW Extension home storage guide waits until half to three-quarters are down. My large onions guide uses the same sign: the tops start to yellow and fall over.
• The neck goes soft. Pinch the neck just above the bulb. A stiff neck is immature. A soft, limber neck is mature. Wind, rain or a dry spell can knock tops over before the bulb is ready, so the pinch is the better check (UGA Extension, quoted in a UMass Extension fact sheet for onion growers).
• The days add up. The Plan My Garden planner counts about 100 days to maturity for bulb onions, and most varieties mature 90 to 120 days after planting (Iowa State). That tells you when to start watching.

Stop watering once the bulbs reach full size and the tops begin to fall (University of Minnesota). Extra water as the crop matures delays curing and causes storage problems, according to Utah State University Extension. If an onion sends up a flower stalk, pull it at the first sign and use it soon, because bolted onions do not store well (Iowa State).

How to pull onions without hurting them

1. Pick a dry day. Dry, cool harvest days limit disease later (University of Minnesota).
2. Loosen, then lift. Loosen the soil with a garden fork or spade and pull the bulbs with the tops attached (Iowa State). Keep the fork away from the bulbs. A stabbed or sliced onion will not store, so put it in the kitchen pile.
3. Brush off the soil. My large onions guide says to brush off any excess soil.
4. Handle them gently. Bruises are direct entry points for disease (UMass), so set damaged bulbs aside for the kitchen.

How to cure onions

Curing dries the tops and outer skins until the neck seals. Spread the onions in a single layer, tops still on, somewhere warm, dry, airy and out of direct sun. Weather changes how long it takes, which is why the sources give different times:

So let the neck tell you when they are done. Roll it between your fingers. If the tissue does not slide, it is tight (UMass). Neck rot and bacterial rots travel through green tissue into the bulb, but not through dry tissue.

Watch the sun. Very hot sun in the 90s can scald the bulbs (UMass), so if your only warm spot is in full sun, use a shed or garage.

Trim, braid or bag

Once the necks are dry, cut the tops off. Sources differ on how much to leave. Iowa State says about 1 inch above the bulb, the same inch my large onions guide leaves. Utah State says 1 to 2 inches. The UMass fact sheet leaves 2 to 3 inches of neck, because the longer neck gives rot farther to travel from the cut to the bulb. Whichever you pick, cut only dry tissue: cutting a top that is still green or moist can bring on neck rot in storage (UMass). As you trim, throw out any onion that shows decay (Iowa State).

All three come from Iowa State, and Utah State also uses mesh sacks. Whatever you use, air has to move through the onions (Iowa State). The UW Extension storage table marks storage onions “no” for plastic bags.

Where to store onions

Onions want it cold and fairly dry, in a basement, cellar or garage (Iowa State). SDSU Extension files bulb onions under “cool and dry”, the same group my vegetable storage chart puts onions and garlic in.

• Keep it under 40°F. Onions start to sprout above 40°F (University of Minnesota). Utah State’s commercial onion guide adds that they sprout and decay rapidly between 40 and 50°F, while 32°F keeps well-cured onions dormant.
• Do not let them freeze. Frozen onions get water-soaked scales (UW Extension). If they are in an unheated garage, move them before it drops below 32°F (Iowa State).
• Keep them dark. Light after curing turns the outer scales green (UMass).
• The refrigerator works, outside the crisper. Most refrigerators are cold and dry, the conditions onions and garlic prefer (UW Extension). The crisper drawer is too humid, as my storage chart notes, and onions tend to mold when moisture is high (University of Alaska Fairbanks).
• Check them. Look them over regularly and throw out any that start to rot (Iowa State). Use softening or sprouting ones first (Utah State).

How long onions last: storage onions vs sweet onions

My vegetable storage chart gives one range for all dry onions, 1 to 8 months at 32°F, from the University of Maine storage chart (built on USDA Handbook 66). The table above splits that by type, which tells you which onions to eat first.

As a rule, sweet onions do not store as well as the more pungent types (University of Missouri Extension). Variety still matters more than the label. ‘Sweet Sandwich’ is one of Iowa State’s longer keepers, and Utah State gives ‘Walla Walla’ and ‘Candy’ 2 to 4 months where Iowa State gives them a few weeks. Check how a variety is described before you count on it for winter.

Onions grown from seed also store better than onions grown from sets (UW Extension).

Why onions and potatoes should not share a bin

They want different air. The University of Maine chart puts dry onions at 32°F and 65-70% humidity and late potatoes at 38-40°F and 90-95% humidity. A bin damp enough for potatoes is the high-moisture setting that makes onions mold (University of Alaska Fairbanks). Onions also give off pungent gases that potatoes and apples can pick up, so UW Extension says not to store them near each other. Give onions their own dry shelf, and see the vegetable storage chart for where potatoes and the other crops go.

Sprouting and neck rot: what causes them

Sprouting means the onions are too warm, were poorly cured or were pulled immature, and new roots mean the humidity is too high (Utah State commercial guide). Move them somewhere colder and drier, and eat the sprouting ones first.

Neck rot is a gray mold (Botrytis) that starts at the top of the bulb, and poorly cured onions are the ones likely to get it in storage (UMass). Prevention starts at harvest:

• Avoid extra moisture near harvest and cure the bulbs well (Utah State).
• Never cut through green tissue when you trim (UMass).
• Avoid bruises and cuts. Black mold, another storage rot, usually gets in through wounds, often at the neck (Iowa State).
• Eat thick-necked, bolted or damaged onions first (Iowa State).

Plan next year’s storage onions

The Plan My Garden planner starts onion seed indoors 12 to 11 weeks before your last frost, transplants 4 to 2 weeks before it, and places 4 onions per square foot (spacing details are on how many onions per square foot). Enter your zip code to find your frost dates and turn those weeks into dates.

I buy onion seed and onion plants from Wood Prairie. Their organic onion seed includes Ailsa Craig, Valencia and Gladstone. Code PMG5 takes 5 percent off.

Quick questions

How long do you cure onions?

Usually 2 to 3 weeks in a warm, dry, well-ventilated spot (Iowa State Extension), until the neck is tight and the outer skins rustle. University of Minnesota Extension allows 2 to 4 weeks at 75-90°F.

Can you cure onions in the sun?

For a few dry, warm days, yes (University of Minnesota Extension). A UMass Extension fact sheet warns that very hot sun in the 90s can scald the bulbs, so a shed or garage is safer for the full cure.

How do you know when onions are cured?

The neck is tight and the outer scales are dry and rustle when you handle them (Iowa State Extension). To test the neck, roll it between your fingers: if the tissue does not slide, it is tight (UMass Extension).

Can you store onions in the refrigerator?

Yes, outside the crisper drawer and not in a plastic bag. UW Extension says most refrigerators are cold and dry, the conditions onions prefer.

How long do homegrown onions last?

UW Extension gives storage onions 6 to 9 months at 32°F and sweet onions 1 to 3 months. Iowa State says Walla Walla and Candy keep only a few weeks. University of Maine’s chart gives all dry onions 1 to 8 months.

Let the planner place them

Next year’s onion bed is easier to get right on paper. Plan My Garden is free to start: enter your zip code, draw your beds, pick onions and everything else you want to grow, and it places each plant at square-foot spacing and builds a planting schedule (start indoors, transplant and direct sow dates) from your frost dates.

Related: Vegetable Storage Chart · How to Grow Large Onions · Harvesting and Curing Garlic · How to Cure Winter Squash