The Vegetable Garden

Can onion sets be saved for next year?

A gardener picks onion sets out of a pot containing dozens of them

Whether you’ve just planted your latest crop and have a few sets left over, or you’re thinking of buying more than you need while a great offer lasts, you’ll be pleased to know that you don’t have to go out of your way to use up all your onion sets immediately.

Storing onion sets properly is a great way to make your money go further when it comes to growing onions. Fortunately, it’s a simple task that practically anyone can do with the right conditions to hand.

How do you store onion sets?

Storing onion sets works on much the same principle as storing harvested onions at the other end of the growing process. Your biggest concern should be getting the conditions right in your storage area, as too much moisture, warmth or cold could cause adverse effects. In turn, this could result in your onion sets going bad before their time. 

The first thing to think about is getting the right container. Onions and onion sets love ventilation to keep them cool and dry, so you don’t want to put them in a solid or sealed container such as a box or jar. Instead, opt for mesh shelves or net bags that hold your onions while exposing them to the air flow of the room. 

If you haven’t kept hold of the mesh bags the sets came in, or have any other mesh bags to hand, here are some alternatives you could try:

  • An unsealed, open top crate
  • A hessian (or similarly porous fabric) bag
  • An old pair of tights

These options can be a good in a pinch, but proper onion nets are still the best choice as they're designed for the purpose.

Once you have your nets or crates - make sure you have enough of them to store all your spare sets - you’ll need to think about where you’ll keep them. As we’ve mentioned, environmental factors can play a huge role in the longevity of your sets, so stick to somewhere cool, dry and well-ventilated. If you’ve chosen an outbuilding such as a shed, be aware that you may need to move your sets during frosty weather to protect them against the cold. 

Good location options for storing your onion sets include:

  • Garages
  • Sheds
  • Unheated rooms of the house such as porches or utility rooms

A pantry can also be a good option, but make sure to label your sets clearly to differentiate them from other foodstuffs to be on the safe side. The same goes for anywhere that you’re also storing other plant bulbs or several varieties of onion sets. Labelling everything up is just good practice in general.

The last step is to regularly check your onion sets for any signs of rotting or degeneration. This could be:

  • Discolouration
  • Squishiness / abnormal texture
  • A sudden, strange smell
  • Evidence of mould or fungal growth on the sets

If you spot any such signs, dispose of the affected sets immediately to prevent the condition spreading through the rest of your stock.

How long can you keep onion sets before planting?

There’s no set period for how long you can keep your onion sets. Depending on the storage conditions, you might find they last six months, or you might find they last over a year. We recommend that you only store a few sets the first time you do it - that way if your conditions aren’t right you haven’t lost a great deal. 

As for an upper bound, we’d advise not to store your sets for two years or longer, as there is an increased risk that they could rot or become barren by the time you come to plant them. 

If you have too many onion sets and storage isn’t an option, here are some ways you could use them up instead of throwing them away:

  • Try growing the onions in a pot or similar container if you’ve no bed space left
  • Offer them to a friend or loved one
  • Give them to a local gardening club or allotment

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