Knowing when to pull onions out of the ground separates a pantry full of firm bulbs from a pile that softens by December. Onions can be eaten at any stage of growth, but storage onions need to reach full maturity, and the timing cues are visible in the foliage and the neck. The same patience that pays off with butternut squash harvest timing applies here: wait for the plant to signal that it is done, then handle the crop carefully so the bulbs keep through winter.
When Are Onions Ready to Harvest?
Harvest timing depends on maturity rather than the calendar. Depending on variety and planting method, onions need roughly 90 to 120 days from sets, and 100 to 150 days from seed, to reach full size. Two visible indicators tell you the bulb has stopped growing: the tops, and the neck.
Two Ripeness Indicators to Watch
- Dried, fallen tops: when at least half of the foliage has yellowed, dried, and toppled over, the bulb is mature. Recommendations on the exact percentage range from 50 percent to 80 percent depending on the source.
- Dry necks: when the neck, the base of the stem right above the bulb, turns from green and fleshy to dry and papery, the onion is ready. Rolling the neck between your fingers confirms it.
Harvest in dry weather. Wet soil and humid conditions increase the risk of spreading disease, and bulbs pulled from saturated ground carry more moisture into storage. The more the onion matures, the more dry matter it contains, which makes it taste sharper and store longer. Dig down beside one bulb and check its size before committing to the whole row. A mature storage onion reaches the diameter its variety is known for, and a bulb that is still small while the tops stay green simply needs more weeks in the ground.
Day-Length Types and Their Maturity Windows
Day-length type sets the growth clock. Short-day onions bulb when daylight reaches about 10 to 12 hours, long-day types need 14 to 16 hours, and intermediate varieties fall between. Match the type to your latitude or the bulbs simply will not size up. Seed catalogs label each variety with its day-length class, so check the description before ordering. A long-day type grown in a southern garden produces greens but few usable bulbs. Spring-planted crops follow the lengthening days, while fall-planted onions in mild climates grow through winter and finish the following spring.
| Day-Length Type | Bulbing Daylight | Best Fit | Typical Use |
|---|---|---|---|
| Short-day | 10 to 12 hours | Southern gardens, zones 7 to 10 | Sweet, mild bulbs for fresh use |
| Intermediate | 12 to 14 hours | Transition zones, zones 5 to 6 | Flexible crops from spring sets |
| Long-day | 14 to 16 hours | Northern gardens, zones 3 to 6 | Storage onions with high dry matter |
Watering stops about two to three weeks before harvest so the bulbs cure in place instead of taking up more moisture. Gardeners who irrigate from collected rainfall can harvest free rainwater for the garden and control exactly when the last watering happens, which tightens the harvest window.
How to Harvest Onions
A gentle lift beats a yank. Loosen the soil around the bulb with a garden fork set a few inches away from the row, then lift the onion by the tops. Pulling hard on green tops tears them off and leaves a bruised bulb that rots faster in storage.
Handle Bulbs with Care
Leave the roots and tops attached at harvest. The foliage continues to feed the bulb during the early part of curing, and cutting it too soon shuts off that transfer. Keep the bulbs out of direct sun for long periods, because sunscald weakens the outer skins and invites rot.
- Choose a dry day that follows a few dry days in a row
- Loosen the soil with a fork set well outside the bulb
- Lift each onion by the tops and shake off loose soil
- Lay the bulbs on the soil surface or on a rack to begin curing
- Bring them under cover if rain threatens
Sort as you go. The largest bulbs are the ones to eat first or use for immediate cooking, while smaller bulbs with fully dried necks have the best storage potential. Onions that send up flower stalks, called bolting, never store well and should be used right away. A thick, green neck at harvest means the same thing: the bulb was not finished and will not keep, so use those onions within a few weeks. Thin-necked bulbs with papery skins are the ones to store.
Curing and Topping
Curing dries the outer skins, shrinks the roots, and seals the neck so moisture cannot enter. Skip this step and even a perfectly timed harvest will not keep.
Curing Conditions
Cure in a warm, dry, well-ventilated place out of direct sun, such as a shed, garage, or covered porch. Temperatures around 75 to 80 F with good airflow dry the bulbs in two to three weeks. Humidity is the enemy: damp curing air encourages neck rot and soft skins. Lay the bulbs in a single layer rather than piling them, because stacked bulbs trap moisture where the skins touch. A spare room with a fan, a screen porch, or even a clean cardboard box in the garage can double as a curing station for a small crop.
How to Tell Curing Is Complete
The neck feels tight and papery, the roots have shriveled, and the outer skin rustles when you touch it. A bulb that still feels moist at the neck needs more time. Turn the onions every few days so every side dries evenly.
Topping for Storage
Once cured, cut the tops back to about 1 inch above the bulb, or leave longer tops and braid the onions for hanging. Either way, keep the roots trimmed short. Trimmed tops can go on the compost pile, and the dried skins make a useful mulch once fully dry. Unlike leafy crops, where harvesting herbs for continuous production keeps plants producing all season, onions are a one-shot crop: every bulb comes out at once and must be cured before it can be stored.
Storing Onions for the Long Term
Storage conditions decide how long the crop lasts. Onions keep best in a cool, dry, dark, and well-ventilated space, with temperatures around 32 to 40 F and humidity between 60 and 70 percent. Warm kitchens and damp basements both shorten shelf life. Humidity swings are harder on onions than steady warmth, so a basement with stable conditions often outperforms a dry heated closet.
Container and Location Choices
- Mesh bags, wire baskets, and slatted crates allow airflow around every bulb
- Pantry shelves work for short-term storage, but warm kitchens shorten shelf life
- Keep onions away from potatoes, which release moisture and ethylene that speed sprouting
- Check the stored crop monthly and pull out any bulb that softens or sprouts
Variety matters as much as conditions. Onions with high dry matter, typically the yellow storage types, keep for months, while sweet, low-dry-matter varieties are best used within a few weeks. The same logic of matching a cultivar to your climate applies when you grow hot peppers from seed to harvest: the right variety for the season makes the difference between a short and a long harvest window.
For onions that will not make it to spring, processing beats watching them spoil. Chopped onions freeze well in bags, and sliced rings dry into instant seasoning. Both routes take an hour on a busy harvest day and empty the storage rack of the weakest bulbs first.
Saving Seed and Planning the Next Crop
Onions are biennials, so saving seed takes two seasons: the bulb must be replanted, allowed to flower, and set seed in its second year. A few plants left for this purpose produce hundreds of seeds, and the flower heads are easy to collect once they dry. Replant the saved bulbs in early spring, spacing them widely so the flower stalks have room to develop.
Collecting and Storing Seed
Choose the best-shaped, disease-free bulbs for seed stock and mark them before harvest. Let the flower heads dry on the stalk, cut them into a paper bag, and rub out the black seeds. Dry them thoroughly before storage in a cool, dark place, and label them with the variety and the year. Keep the seed-stock plants separate from the eating crop so you never pull the wrong bulb. Gardeners who save their own seed enjoy the same self-sufficiency as those who grow chickpeas at home for a bountiful harvest, because both practices cut the annual seed bill and preserve the varieties that perform best in a local garden.
Once the onion bed is cleared, the space can go straight into a follow-on crop. Warm-season vegetables and quick greens both fit the gap, and succession planting methods keep the garden producing through the year instead of resting empty after a single harvest. Moving onions to a fresh bed each year also reduces soil-borne disease pressure, and the cleared rows give you a head start on the next planting.