How to grow onions from onion sets for a fantastically flavourful crop

If you want to learn how to grow onions, you absolutely need to get to grips with onion sets: they are one of the best and easiest ways to get your own delicious crop of oniony goodness on the go!

Now, we all know that edimentals are big news in the gardening world at the moment – not least of all because growing our own fruit and vegetables is a savvy way to save money in this ongoing cost of living crisis.

So, with that in mind, here's how to transform a corner of your garden into a thriving onion plot...

How to grow onions from onion sets

If you're trying to suss out how to grow onions, most experts suggest that you swap that packet of onion seeds for an onion set instead.

'Onion sets are basically immature onion bulbs,' says Christopher O'Donoghue, one of the co-directors of Gardens Revived, 'and they are, without a doubt, one of the easiest and fastest ways to grow onions.'

Christopher O'Donoghue

A gardener with over a decade of experience under his belt, Christopher set up Gardens Revived with his brother, Andrew, in 2018 to create a thriving family business. Together, they have worked on residential gardens, listed buildings and gardens, flower shows and large estates with some exceeding 70 acres – many with historical significance.

The benefits of using onion sets over onion seeds are manifold. They're less likely to be affected by disease, for one, and they always result in an earlier crop. They're also ridiculously easy to suss out, too, even for the very greenest of gardeners.

What's not to love? Look this way if you want to learn how to master the art of the onion set, then...

What you will need:

When it comes to learning how to grow onions, the first thing you'll need to buy is an onion set. 

Here are just a few of our favourite options:

• Thompson & Morgan: a wide variety of onion sets
• Crocus: a great selection of onion sets
• Amazon: a surprisingly good selection of onion sets

You will also need to pick up the following:

• A good weeding tool, like the Telescopic Carbon Steel Garden Weeder from B&Q
• A spade, like the Spear & Jackson Select Carbon Digging Spade from Homebase
• A peat-free soil-based compost, like Miracle-Gro Premium All Purpose Compost from Amazon
• A high potassium general fertiliser, such as Vitax Q4 from Amazon

How-to guide:

Keen to learn how to grow onions from onion sets, then? Look this way...

1. Prepare the area

Onions have limited root systems, so it's important to give them the best possible start to life.

'Find a sunny spot with well-draining soil, and weed the area thoroughly,' advises Christopher.

It's also a good idea to boost the quality of the soil by mixing in a good peat-free compost, and you can also apply a high potassium general fertiliser, too.

2. Get planting

Learning how to grow onions is unexpectedly easy, largely because the planting process is so simplistic.

'Push them 2cm deep into well prepared, loose soil in a row, spacing them about 10cm apart, and gently firm them in,' advises Morris Hankinson, founder of Hopes Grove Nurseries.

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants, which he established after graduating with a Commercial Horticulture Degree from Writtle College, Essex in 1992.

'If you are growing a lot of onions, then space the rows 30cm apart so you have space to get in between for weeding,' continues Morris, noting that 'onion plants don’t cast much shade so weeds can do very well in between them!'

3. Protect them at all costs

Morris says that you should water your onions well, to help them settle in, and suggests covering them with a protective garden fleece from Amazon to keep hungry birds at bay – just until everything is safely rooted in.

4. Wait patiently

The best bit about learning how to grow onions? Eating them, of course! However, knowing when to harvest onions will depend on when you plant them: if you plant yours in the autumn (sometime between late September and early November), they should be ready by June or July. 

If you're happy to wait for late-summer onions, however, you can plant them between March and April.

FAQs:

And just like that, you've learned how to grow onions from onion sets! We promise that your soups and pasta sauces will never be the same again...