How to Grow Onions

How to Grow Onions – which is what many gardening articles will help with but also in this one, a bit of Onion History.

Why? Because I’ve picked out some of the interesting snippets for you, so that you can sit in a comfy chair, read all of his Plews Potting Shed blog and feel you’ve spent your time well. Or you can skip to the bits on how to grow onions, read that, then go out and get gardening. Either way, you’ll end up knowing your onions (more on the origins of that phrase below)

Onions – a Bit of History

Did you know that onions were used as part of the mummification process in ancient Egypt?

Like many other early civilisations, the Egyptians saw the onion as a symbol of eternity. Those rings within rings layers of flesh suggesting there was always another part of life to be found and lived. Because of these magical qualities, onions would be placed in the thorax, pelvis and near the ears and eyes during the mummification process.

In Egypt, the cultivation of the onion can be traced back to 3500BCE. However, records of onions growing in Chinese gardens go further back, to 5000 BCE.

The Romans liked onions, leeks and garlic too. Pliny the Elder recorded six different varieties which were grown in the Roman Empire including in Pompeii gardens. During excavations at Pompeii, archaeological evidence was found to support his writing as onion bulb shaped cavities were discovered in the gardens.

Pliny also wrote of the onion’s medicinal properties. They were thought to cure dysentery, heal mouth sores and dog bites and even reverse baldness. If any of you wish to try this, mix onion juice with honey and rub onto a bald patch vigorously. I haven’t tried this, so can’t guarantee its efficacy!

Modern science agrees with the excellent antiseptic, antibacterial and diuretic properties of onions. One of the traditional recipes for relieving coughs, colds and earache was to eat a roasted onion or drink onion juice. Onions also have anti-inflammatory qualities, which may explain why the Olympic athletes of Ancient Greece would rub onion juice on their bodies before competing.

How to Grow Onions – a Bit of Helpful Botany

The onion is a member of the Allium genus, which has over 500 species.

Onions, Allium cepa, are also known as the bulb onion or common onion. ‘Common’ as in the most widely grown and eaten member of the Allium family. This is a cultivated onion species, although it is thought to have about four of the wild species in its ancestry.

We tend to grow it as an annual vegetable, and harvest the bulb for food. However, the onion is actually a bi-ennial plant. If left unharvested, a stem develops from the centre of the bulb over winter, to flower the following year. If you want to collect and grow your own onion seeds you should let at least one of your onion plants overwinter and flower. The seeds are triangular shaped, and glossy black.

Should you use seeds or sets?

You can grow onions from seed or by planting ‘sets’. Using seed is cheaper and gives you a wider selection of varieties to choose from. Many heritage varieties of onion are only available as seed.
However, onion sets, which are basically baby onions, are easier for the beginner gardener. They’re also useful for those gardeners who have less space to sow and grow on the seeds. And if you garden on clay you’ll find that onion sets are more tolerant of these heavier soils.

Sowing Onion Seeds

This can happen in the autumn or in the early spring.
Sowing overwintering onions will give you an earlier crop the following year.
If your soil gets very waterlogged over the winter, you may be better sowing the onion seeds in a raised vegetable bed.
If you’re sowing the seeds in the spring, then covering the soil with cloches or horticultural fleece over winter, ensures the seeds have a warm soil, which aids germination.

Growing Onions from Sets

Most people plant onion sets in the spring. In a cold spring, you can start your onion sets off in a cold frame, cool greenhouse or cloche. Popping them into egg boxes means there is no root disturbance when you come to plant out the onions in the ground.
Planting the sets in the autumn will give you an earlier crop, but may require cover in a wet winter. The warm damp soil of an autumn planting does encourage good root establishment.
When you plant the onions, leave just the tips exposed. If the sets do get dug up by birds, cats, dogs or foxes then just press them back into the soil.

General Advice on How to Grow Onions

Onions are amenable to being grown using various methods of cultivation. For example –

Growing onions in long straight rows in the ground
Using the square foot method
Growing in a raised bed
No-dig methods of cultivation
Interplanting with other crops
As companion plants

Planting in rows is the most usual method of cultivation where onions are grown in the ground. This works rather well as they can be interplanted with a longer maturing crop; one of the brassicas, for example, brussels sprouts works well. The sprouts would be planted the ‘correct’ distance apart and the onions would line up between two rows of sprouts.

Mulching the soil around the young onion plant will help to keep moisture and warmth in, and reduce watering requirements. As they grow and mature, scrape the mulch away so the bulb is exposed to the sun.

Perversely, onions don’t like to be too wet, so they do need a free draining soil. Where your soil is not as free draining or as fine a tilth as onions prefer, it may be advisable to grow them in raised beds. This has the added advantage of closer spacing of your crop, so you’ll harvest more onions from the same area. For example if you’re using the square foot method and ‘average sized’ onions, you’ll get 4 mature plants in a square. when growing in the ground, you can create raised rows to help improve drainage, planting the onions on the mounds.

Companion Planting

Normally, it is members of the onion, or allium family, who benefit other plants. for example, roses and strawberries. However, growing parsley near them is said to help keep the onion fly away.

Harvesting Onions in July and August

Watch out for the leaves of onions turning yellow – this means they are nearly ready to harvest.

The crop should be harvested after the tops have bent over naturally and the leaves have begun to dry out and rustle.

After lifting, the onions should be spread out in the sun to dry. In wet summers, you’ll need to dry them under cover; otherwise they can be left on the earth to dry.

Storing your onions in a rope is traditional and easy to do.

Use either untreated natural string or strong raffia
Tie two together by their dried leaves to form the base
Build up the rope one onion after another upwards so they lightly touch
Finish with a firm knot at the top, leaving enough string to make a loop to hang the ‘rope’ on
Hang in a frost free potting shed, outhouse or garage

Hanging them means air is able to circulate around the onions keeping them fresher; and they’re easy for you to cut and use when needed.

As for ways of eating your onions after you’ve grown them in the garden, the methods are numerous; they are such an adaptable and essential vegetable!

Knowing your Onions

You may know the phrase ‘knowing your onions’, but from where and how did it originate?

Well, it has nothing to do with how to grow onions. The first known use of the phrase in print was in 1920s America. And it seems to have less to do with gardening and more to do with the craze for “in” phrases such as something being ‘the cat’s pyjamas’.

‘Knowing your onions’ refers to a person being knowledgeable about any given subject, or having excellent general knowledge. Although if you know the difference between onions, leeks, shallots, garlic, clumping onions and all the rest of the Allium family – it’s a fair bet that you do indeed ‘know your onions’!

If you would like help with learning more about your garden and gardening, why not ask about our bespoke Gardening Lessons, where your classroom is actually your own garden. We can help you learn gardening basics, carry out worm and other experiments and also show you how to plan an ornamental border or kitchen garden.

And for further gardening advice and inspiration, check out Plews Potting Shed blogs, including the selection below and our monthly Tipsheet – You could come and find us on Instagram Pinterest and Facebook too.