Onions, garlic and shallots will often be ready to harvest in your polytunnel in around July, earlier than those grown outside. Clearing these out this month will allow you to get crops in place for overwintering in your protected space. But in order to get the most out of this harvest, it is important to know how to harvest and store onions for later use. Onions can be stored for use over the summer, autumn and winter months, but it is important to prepare and store them correctly.
Gardeners in the past were often recommended to bend over the foliage of onions and other alliums when the time to harvest drew near. But it is now generally felt that such measures are unnecessary. Now, it is usually considered to be best to wait until the foliage turns yellow and flops over, to wait a week or two, and then to harvest your onions.
Harvest and Store Onions
When harvesting onions, simply ease them from the soil. Try to be as gentle as possible when harvesting onions and other alliums, as any bruising or damage can reduce the length of time for which the onions can last in storage. Once you harvest your onions, you will need to decide how to store them. Onions and other alliums can be stored for later use in a range of different ways.
Checking Harvested Onions
It is important to check over the onions that you have harvested carefully for any damage, or signs of pest of disease. Any blemished onions should be eaten or preserved right away, as these will not last as long in storage. Sort your harvested onions according to when you will eat them, keeping the best specimens to be stored for the longest period of time.
Drying Harvested Onions
One of the easiest and most straightforward ways to store onions is to dry and hang them in traditional braids or in netting (or old tights). The first step in this process is to dry the onions. Your polytunnel is an ideal place to do this, especially if you have erected some staging or a hanging shelf on which you can place your onions in a single layer to dry. Onions for storage should be left to dry for at least 2-3 weeks. (If you want to braid your onions, leave some stem on the bulbs.)
To braid your onions easily, make a loop of twine or string. Starting at the bottom of the loop, wind the stem on the bulb in a figure of eight around the two sides of the loop. Continue to add onions to the loop by winding the stems in a figure of eight around the string. These strings of onions can then be hung in a cool place out of direct sunlight, and onions can be cut from the string as and when needed over the months to come.
Of course you can also simply hang your onions in netting or tights, which will allow for good airflow. Tie a know between each onion, so they can be cut away when needed without disturbing the rest of the string.
Check out our grow guides to learn more about growing, harvesting, storing and cooking the crops you grow in your polytunnel.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.