Your Guide to Growing Onion Sets Successfully
Onions are an integral ingredient for almost any type of culinary delight, and they can be a lot easier to grow than people expect. Growing onions and shallots from sets is a great, fuss-free and low-risk way to grow your own produce that will make both beginner gardeners and seasoned growers equally excited. Here’s our quick guide to planting and growing sets.Â
What are onion sets?
‘Sets’ offer a speedier, simpler, and more successful way to grow onions and shallots than traditional seed.
They are very small, dormant bulbs that have been grown from seed and harvested early. They have been dried to suspend the growth process, and will resume when they have been planted in the right conditions to grow into full-sized onions and shallots.
Depending on the variety, onion sets can be planted in autumn for overwintering or planted in spring. The process for planting is the same.
How to plant onion sets
Alliums love to grow in firm soil that holds its moisture, so it’s important not to loosen the soil too much before planting. Sets do not need to be soaked, meaning they can go into the ground straight away.
Plant your onions 10-15cm apart just below the soil surface, and make there’s around 30cm between your rows. Shallots need a little more room as they grow in clusters, so leave 15-20cm between each set.
Your alliums will do better with lots of nutrient-rich organic matter like garden compost, so be sure to give them the boost they need. You could also use our compost improver to help the process. Â
Sometimes, birds can pull out freshly planted sets to investigate whether they can eat them or use them for nesting materials.Â
To prevent this happening, you could choose to protect your sets with our easy-net tunnel or some horticultural fleece until they’ve developed roots that are strong enough to hold them in place.Â
How to look after your onion plants
Keep carefully weeding your onions as they do not grow well when in competition with other plants. Their thin, upright leaves provide little cover and allow smaller plants to leach the nutrients. As onions and shallots are not deeply-rooted, it is also important that you do this delicately to avoid damaging or accidentally uprooting your bulbs. Avoid hoes and use your hands for best results.
Make sure you water your onions during dry spells, especially when they are forming their roots, but try to avoid getting the foliage wet as this can lead to fungal diseases. Once your bulbs have swollen in mid-summer, we recommend that you stop watering them so that they are easier to store.
It is also imperative that you avoid your onions bolting. This is where they start to flower, and the energy is drawn away from the bulb essentially stunting its growth. They will also make your onions more difficult to store.
If you see a flower, remove it immediately to allow your bulb to continue swelling.Â
Harvesting your onionsÂ
If you planted overwintering sets, then these will likely be ready to harvest in June and July, whilst spring-planted sets are ready from July to October. You’ll know when your onions are ready to harvest as their foliage will turn yellow and the foliage will topple over. Do not bend the necks of your onions yourself as this can damage the bulb and cause disease, and harvest your crop before the foliage turns brown.Â
To harvest, choose a dry day and use a fork to very gently lift the bulbs, taking care not to damage or bruise them as this will mean they won’t store properly.Â
Storing your onionsÂ
First, you need to dry your onions out for around 2 weeks. Lay them on newspaper or racks and keep them nice and dry - you’ll know when your onions and shallots are ready to store as their skin will be papery and they will rustle when you touch them.
You can store them in nets or plait them together, hanging them somewhere cool and dry with good ventilation to discourage sprouting. If stored correctly, your onions can keep for a number of months.Â
Growing onions and shallots from sets has never been more straight-forward, so why not take advantage of our great range of varieties and grow your own this year?Â
