When to Harvest Onions
Onions are ready to lift when their tops naturally yellow and flop over, usually from July into September depending on variety and planting time. Harvesting at this stage, followed by thorough curing, produces firmer bulbs that store far better. Dry weather, gentle handling and good airflow make the crucial difference.
Start checking onions from July, though exact timing varies with variety, sowing date, sets or seedlings, and local weather. Bulbs are approaching maturity when their necks soften, leaves yellow and the tops naturally bend over near the base. Do not force this by treading on foliage or snapping stems early. The plant needs its leaves to finish feeding the bulb until it is ready. A few plants may flop before the rest, so wait until most of the row shows the same change. In northern gardens or a cool wet summer, ripening may be later. Note the variety and planting date, but let the foliage and bulb condition make the final decision.
Reduce watering as bulbs begin to swell and stop routine watering once many tops are yellowing, unless drought is extreme. Clear weeds gently so air moves around the bulbs, but avoid disturbing roots repeatedly. If prolonged rain is forecast and most tops have flopped, lift the crop rather than leaving mature bulbs in saturated soil. Choose a dry day if possible. Loosen soil beside each bulb with a hand fork, taking care not to pierce it, then lift from underneath. Do not tug hard on the foliage, as a broken neck makes handling awkward. Shake off loose earth by hand and keep the skins dry. Never wash storage onions after lifting.
Check bulbs as you lift them and separate damaged or unusually soft ones. Sound onions should have firm flesh, an intact base and dry-looking outer skins beginning to form. Use bulbs with cut skins, bruises, thick green necks or signs of rot first, as they are poor candidates for long storage. Leave the foliage and roots attached while the onions cure. If the weather is dry and settled, lay bulbs in a single layer on clean, dry ground for a day or two, protecting them from dew and rain. In unreliable British weather, move them immediately to a covered, airy place such as a greenhouse with ventilation, porch or dry shed.
Cure onions for two to three weeks, or until the outer skins are crisp and the necks are completely dry. Spread bulbs on mesh, slats or a rack so air reaches beneath them; avoid deep piles where moisture becomes trapped. Keep them shaded from strong sun, protected from rain and well ventilated. Turn bulbs gently every few days if they are laid flat. Check for soft patches, mould or an unpleasant smell, removing affected onions promptly. Drying may take longer in humid weather, so do not rush them into storage because their leaves look dry on the outside. A properly cured neck should feel thin, papery and closed.
After curing, trim roots lightly and cut dry foliage with clean secateurs, leaving a short neck. Alternatively, braid fully dried onions with supple but dry foliage, ensuring the bulbs are not bruised. Sort the crop by condition. Eat large, damaged or thick-necked bulbs first, then use medium bulbs, reserving only the firmest, soundest onions for long-term storage. Do not compost bulbs showing rot or persistent disease symptoms; dispose of them with household waste where appropriate. Clean the storage area and tools before bringing in the best bulbs. Record which varieties stored well, since keeping quality varies greatly even when onions are cured carefully.
Store cured onions in a cool, dry, dark place with steady airflow. Use mesh bags, netting, open crates or shallow trays, and avoid sealed plastic containers. Do not store them beside potatoes, which release moisture and can shorten onion storage. Inspect the crop every few weeks through autumn and winter, removing any bulb that softens or sprouts. A dry spare room, frost-free outbuilding or airy cupboard may work better than a damp shed. If conditions are humid, use onions sooner rather than expecting every bulb to last. Good storage starts in the bed, but careful curing and regular checks protect the harvest.
Frequently asked questions
Should I bend onion tops over to make bulbs ripen?
No. Allow foliage to yellow and flop naturally. Bending or treading on leaves early can interrupt the final transfer of energy into the bulb and may create an entry point for rot. Once most tops have naturally fallen and yellowed, reduce watering and prepare to lift the crop in dry conditions.
Can I leave onions outside to cure?
Only during a reliably dry spell, and even then protect them from dew and rain. British weather often makes an airy covered place more dependable. A well-ventilated greenhouse, porch or dry shed works well. Spread bulbs in a single layer, keep them out of direct hot sun and bring them inside before wet weather.
Why are some onions sprouting in storage?
Sprouting can follow incomplete curing, warm storage, fluctuating conditions or a variety with limited keeping quality. Use sprouting bulbs promptly. Next season, wait until necks are fully dry before storing, choose a cool airy location and keep the firmest bulbs for storage. Regular checks prevent one failing onion affecting its neighbours.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 19 Sep 2026.