When Should I Harvest My Onions?

Getting the harvest timing right is one of the most important — and most misunderstood — parts of growing onions for storage. Harvest too early and the neck is still thick and soft, meaning the onion will rot in storage; wait too long and rain and pest damage begin to take their toll. The good news is that the onion itself gives clear, reliable signals when it is ready, and once you know what to look for the timing becomes straightforward.

The main indicator: tops falling

The primary signal that maincrop onions are approaching harvest readiness is the folding over of the leaf tops. As the onion reaches maturity, the bulb stops taking on more nutrients and the flow of water and carbohydrate through the neck slows. The neck begins to weaken and the leaves soften at the point just above the bulb, causing them to naturally fold over and lie on the ground rather than standing upright. This is not disease — this is the plant indicating it has finished growing. Wait until roughly half to three-quarters of the tops in the bed have fallen before beginning to harvest. This typically happens from late July to mid-August for spring-planted sets in the UK.

The neck test

The most reliable individual test is the neck — the dried stem area at the top of the bulb. Grasp the neck of an onion whose tops have fallen and bend it gently. A ready-to-harvest onion has a neck that is clearly beginning to thin, feels dry rather than spongy, and offers no resistance. An unready onion has a thick, still-green or pale-green neck that bends but feels firm and sappy. Never store an onion with a soft, green, or thick neck — it needs more time in the ground or more curing time after harvest before it is safe to store.

Should I bend the tops over?

Some gardeners deliberately bend tops over to accelerate the signal of maturity. This is not recommended as it can damage the neck and create wound entry points for disease. Allow tops to fall naturally; the process cannot and should not be rushed. If you are in a hurry because autumn is approaching, harvest as soon as the majority of tops are down, and complete the curing process under cover.

Practical harvest day advice

Choose a dry, settled spell to harvest. Loosen the soil beneath the bulbs with a fork, lifting rather than pulling — pulling damages the neck. Lay the onions in a single layer on the surface for a day or two if dry and sunny, then move them under cover for full curing. Never leave onions in the ground through wet autumn weather after maturity — they will simply start to rot. The harvest window is real but finite; act when the signs are clear.