If you have grown onions this year, you may be happily pulling them up about now and hopefully celebrating rather lamenting their size. When onions are ready for harvest, their stems and leaves flop to one side as below:
However, just like garlic, there is an important step between harvest and storage, and that involves curing. Onions should be left to cure so that their outer layers of skin dry and they can be stored successfully. This can take a couple of weeks after harvest. Keep the leaves on the bulbs to dry post-harvest, as chopping them off now runs the risk of introducing bacteria to the onions, which might spoil your crop!
There are different ways to store onions while they cure. If you are guaranteed dry weather, you can leave them on the ground where you have pulled them. This is the easy option, but you run the risk of them being eaten by animals, or them rotting on one side if they get damp.
Onions are best dried in a cool, but not cold, dry area, with sufficient air circulation. You could store them outside if the weather is fine, out of direct sunlight, on makeshift racks of trellis or wire frames. This keeps them off the ground and the air flow moving. Alternatively, suspend a pole horizontally and hang bunches of onions from it. These options are cheap and relatively quick to prepare, and will not take up much space.
If you cannot guarantee that your crop will not get wet if left to cure outside, it is best to bring them undercover. Layer them over raised benches in a greenhouse or shed, or covered frame. These can prove a surprising efficient drying tool, as you can hang the onions upside down through the cracks in work benches and pallets. If you have old fashioned crates that stack on top of each other, these will also work well for drying multiple onions at a time.
Alternatively, if you are good with your hands, you might consider braiding the onions together in a bunch and hanging against a wall. This is a very attractive way of drying your onions, and once the curing is complete, you can easily harvest them from the braid as and when you need them.