How to Harvest Onions and Cure Them Properly
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Learning how to harvest onions is mostly a matter of reading the plant. The tops tell you when the bulbs are ready to come out of the ground, and the curing period that follows decides how well they keep. Pulling too early or leaving them too long in wet soil both cause problems. This guide covers the signs to watch for, how to lift the bulbs, how to cure them, and which ones to set aside.
Quick answer
- Harvest when most of the tops have fallen over and started to turn brown.
- Lift the bulbs in dry weather, and bring them somewhere dry and well ventilated.
- Cure for two to three weeks until the tops and necks are fully dry and the outer skins rustle.
- Set aside bruised, cut, or thick-necked bulbs for early use rather than storage.
Why the tops are the signal
Extension guidance relies on the foliage as the signal. Iowa State University Extension states: “Dry or storage onions should be harvested when the tops have fallen over and start to turn brown.” Illinois Extension gives a similar signal and a rough calendar for many gardens: “Harvest in late July or early August, when most of the tops have fallen over.”
Use the tops and the calendar together. A bed where most tops have fallen will usually be ready within a few days, while a bed where the foliage is still upright needs more time. Watch the weather too. Illinois Extension warns that onions should be harvested “before the fall rains” because mature bulbs “will rot quickly in cool, wet soil.”
How to lift the bulbs
Once the tops have fallen, loosen the soil with a garden fork before pulling. Working the fork in a few inches away from the bulbs reduces the chance of cutting or bruising them. Lift each bulb gently by its tops and shake off loose soil. Shake off loose soil and let the bulbs begin to dry before curing.
Handle the bulbs with care. Bruised skin and cut roots create openings that make the bulbs more likely to rot in storage. Set aside any bulb that is damaged while you lift it, so it does not sit with the good ones.
How to cure onions
Curing is the step that turns a freshly lifted onion into a bulb that can be stored. Iowa State advises: “Cure the onions for two to three weeks until the tops and necks are thoroughly dry and the outer bulb scales begin to rustle.” Illinois Extension describes the same need in other words: “Full air circulation for 2 to 3 weeks is necessary for complete drying and curing.”
The place you cure them matters as much as the time. Iowa State recommends that you “dry or cure the onions in a warm, dry, well-ventilated location, such as a shed or garage.” Spread the bulbs in a single layer or hang them in loose bunches so air can reach every side. Check them every few days for soft spots.
You will know the curing is done when the necks have dried fully and the outer skins feel papery. Illinois Extension says the bulbs should be “Leave undisturbed until the outer skin becomes papery and crispy dry.” Do not rush this stage. Bulbs that go into storage with wet necks are the ones most likely to rot at the top.
Which bulbs to set aside
Not every onion is suited to long storage. Illinois Extension advises: “Do not try to store bulbs that are bruised, cut, or diseased or those with green tops or thick necks.” Illinois Extension lists thick necks alongside bruised, cut, and diseased bulbs in the same warning.
Use the set-aside bulbs first. Cook with them soon after curing, and keep the sound, well-cured bulbs for the longer stretch. Sorting at this stage saves you from finding rot in the middle of winter. For the storage side, see our guide to storing onions, and if you are planning next year’s crop, our guide to growing onions from seed covers the start of the season.
Common mistakes during harvest
Most problems come from timing or handling. Pulling the bulbs before the tops have started to fall means the bulbs may be underdeveloped. Waiting too long in wet weather lets the bulbs begin to rot in the soil. Each of these mistakes is easier to avoid if you check the tops and watch the forecast before lifting.
How to tell if a bed is ready
Walk the bed and look at several plants rather than one. Some bulbs in the same row can be ready before others. Take a few bulbs that look ready, lift them, and check the necks. If the necks are soft or the tops are still green, wait several days and check again. A simple test like this prevents pulling the whole bed too early.
How we chose
We limited this guide to two university extension sources that were available and readable on the check date: Iowa State University Extension’s “All About Onions” page and Illinois Extension’s onion page. We kept only statements that appear in the fetched text of those pages. Where a detail came only from a search snippet, or where a page did not load, we left it out. The guide does not rely on retail product pages or general gardening blogs for harvest timing or curing.
Where the two sources gave slightly different wording on timing, we used the more specific signal, which is the fallen and browning tops. We did not invent a combined number that neither source states.
What we could not verify
We could not use the University of Minnesota onion page, which returned a 403 error on the check date. We also could not use an Iowa State news item, which returned a 404 error. Some secondary sources mention planting dates or tops-down thresholds that differ from these; we left them out because we could not open their full text.
What the sources do not say
The two sources we opened do not give a single exact harvest date for every region, and they do not describe how to cure onions in a damp climate with no shed or garage. They also do not state how long a cured onion will keep in storage. Where your conditions differ, rely on the tops, the neck, and the feel of the outer skin.
Frequently asked questions
When should I harvest onions?
Iowa State University Extension advises harvesting when the tops have fallen over and begun to turn brown. Illinois Extension notes that most gardens reach this point in late July or early August.
How long should onions cure?
Both sources point to two to three weeks of curing in a warm, dry, well-ventilated place until the necks are dry and the outer skins rustle.
Should I wash onions after lifting them?
The sources we opened do not call for washing before curing. Shake off loose soil and let the bulbs dry, because wet skins take longer to cure.
Can I store an onion with a thick neck?
Illinois Extension advises against storing bulbs with thick necks, green tops, bruises, cuts, or disease. Use those bulbs first.
What happens if I harvest too early?
Illinois Extension warns that early harvest can leave bulbs that do not dry well. Check the tops and necks before lifting a bed, and wait several days if the necks are still soft.
Sources
- Iowa State University Extension and Outreach, “All About Onions,” yardandgarden.extension.iastate.edu/how-to/all-about-onions (opened 2026-10-27)
- University of Illinois Extension, “Onion,” extension.illinois.edu/gardening/onion (opened 2026-10-27)
