Onion Harvesting and Storing Masterclass

Globally, onions are second only to tomatoes in terms of production – we can’t get enough of them! To get the most from your onion crop you’ll need to store those beautiful bulbs for as long as possible. It’s very easy to do if you follow these simple steps…

When to Harvest Onions

I love growing onions. It’s genuinely joyous to watch those glorious bulbs swell within a matter of weeks. I use the multi-sowing technique to grow them in groups of four or five. Growing this way means I can get many more onions into my space and ramp up productivity in a relatively small area.

You can tell onions are nearing harvest when the leaves begin to flop over. The neck of the bulb where the stem meets the bulb begins to soften, causing the leaves to bend over. From this point on they are contributing less and less towards swelling the bulb and the onion is starting to prepare itself to shut down for the colder months – which is good news for us!

The onions should be ready to lift within a couple of weeks from this point. At this point you’ll also notice the skin of the bulb starting to colour up – an encouraging sign that you’re good to go.

You can, of course, harvest onions to use fresh at any point before this. But if you’re looking to store your crop, then it’s important the bulbs are fully mature.

How to Harvest Onions

In an ideal world it’s best to harvest onions after a couple of days of dry weather. This will give slightly cleaner bulbs, makes them easier to lift, and helps to speed up the drying process.

To harvest, just grab the bulb or the base of the stem firmly, then twist and lift. If you find the bulbs are a bit resistant, or you’re worried about damaging the onion, use a hand fork to loosen the soil around the bulb and encourage them free.

Try not to damage the leaves or roots because these are both important in the next step, which is curing the bulbs to prepare them for storage. We need our onions intact so they can continue to shut down naturally, because this will help them to store for as long as possible. For this reason, I’d also advise against cleaning your bulbs. You can lightly brush off any bigger clumps of dirt if you want, but delay the full cleanup process until after they’ve cured.

Only cure and store good, healthy bulbs. Any that are very small, damaged, or that have produced a flower stalk are unlikely to store for long, so they should be used up as soon as possible. You can always pop them in the fridge to keep for at least a couple of weeks.

Curing Onions

Curing onions creates a seal of papery layers around the bulbs, just like those you get in grocery store onions. These layers keep the bulb drier, helping to prevent any potential bacteria or moulds that could cause the bulbs to soften and go bad. Curing also helps to develop a deeper flavour, so your onions transition from sweet to more aromatic.

To achieve a decent cure, you need to keep your onions somewhere completely dry, with plenty of air circulation. If you are gardening in a reliably warm and dry climate then you may find that simply leaving your onions on the soil surface, out in the sun, works just fine. But if your climate isn’t reliably dry, or if there’s rain forecast, bring them under cover straight away.

You can cure onions in any dry, well-ventilated space that’s sheltered from the rain would do – a porch, lean-to, garage, or perhaps under a miniature polytunnel off the damp ground – anywhere dry with good airflow. I dry mine on a raised platform in the greenhouse, which really helps with airflow. The added warmth speeds things along too.

Lay your onions out so they aren’t overlapping too much. Take care to always handle onions delicately, avoiding any thumps or drops that could bruise or damage your precious haul.

Curing onions takes anywhere from a couple of weeks to a month. I usually play it safe and go for the full month. At this point the leaves will have shrivelled up, the roots will have turned wiry, while the skins should be richly coloured and papery.

Once they’re at this stage, it’s time to clean up the bulbs. Remove any loose skins or, if you wish, peel back the outermost skins to leave pleasingly clean-looking bulbs, though I prefer to keep as much of the skin on as possible to help with that moisture-resistant seal. You can also trim off the roots to a stump and cut the old foliage back to the neck of the bulbs, taking care not to cut into the bulb itself. If you want to store your onions in strings, however, leave about 6in (15cm) of the foliage as we’ll need to use this for weaving them into the strings.

4 Ways to Store Onions

Fully cured onions can be stored in breathable sacks or net bags. Carefully place them in there one bulb at a time, to avoid bruising, and set aside any that have become soft since harvesting to use immediately.

Another option is to simply tie bunches of onions together by their leaves. It’s quick and convenient, and allows for more of that all-important airflow as every onion is fully exposed to the air.

You could also store onions in old pantyhose either in small clusters of bulbs, or individually by securing a knot in between each bulb to physically separate them. The bulbs can then be snipped free, one at a time, to enjoy as needed – certainly a quirky, but no less practical, way to store your onions!

But my favourite and - you have to admit it - the classiest way to store onions is in strings. They just look so magnificent! Start with a length of strong string or twine. I find working from a hook or nail is easiest. Start by just looping some string up and over the hook, then tie the ends together. A length of string about four feet (just over a metre) long is good, to give a string height of half that when the ends are tied.

To place the first onion, create a slip knot at the bottom of your strings then feed the onion into the loop. Bend the foliage and gently tug down to tighten the knot and secure the onion into place. It’s best to use a larger onion for this first one, to help anchor the string down, ready for the rest.

Feed the foliage of the second onion through the two strings, then carefully bend the stem back on itself to tuck in beneath the bulb, which will help weigh it down to hold it in position. Add each successive onion in the same way – place the stem through the strings, bend it back around the string and tuck it under the bulb, pushing it down a little so it’s nice and snug. Rotate the position of each additional onion to create a spiral effect, so that each onion sits neatly.

Whatever method you use to store your onions, move them to a cool, dry place with good air circulation. They don’t need to be kept cold, so somewhere like a basement, frost-free outbuilding, or even a cooler room in the house, out of direct sunshine and away from areas of high humidity, would work just fine.

Keep sack or net-stored onions off the ground away from vermin. Check them from time to time, removing any bulbs that are starting to go soft or mouldy. Onion strings or onion bunches can be suspended from rafters or hooks. Take onions from the top of strings first, working down over time, so they continue to hold together.

Well-stored onions will potentially last right up to the following spring, bringing you tantalisingly close to next year’s harvest. Do drop me a comment below if you have any questions or to share how and where you store your onions.

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