Onions are one of those vegetables that many people all over the world use every single day in their cooking. I personally find onions, whether a standard brown, red or spring varieties very tasty in anything I use them in when cooking-whether soup, stew or salad to name three uses. While I don’t have any growing at the moment, I plan on growing some later in the year.

The binomial name of onions is Allium Copa, and it belongs in the Alliaceae family that also includes things like leeks, garlic and chives. Onions are grown for their bulbs which we eat. The Ancient Egyptians grew them for food, but also for the mummification process.

There are a wide range of onion varieties, which will vary by country as well as by the general use of them. There are bulb or common onions, which are classified according to their colour, shape, the strength of its flavour, and also season. The season relates to early season (short day length for bulb growth), mid season (intermediate day length for bulb growth) and late season (long day-most daylight needed for bulb growth). Spring onions are immature inions, harvested for the shoots and used mainly for the shoots. There are also pickling onions.

Cultivation

Onions do require a space that is open and sunny to thrive. The soil needs to be fertile and free draining. Here is Sydney, onions are better being grown in the winter as onions are generally a cool season crop, although spring onions can be grown here all year round, which I like as spring onions are my favourite.

In southern areas of Australia, where there are at least fifteen hours of daylight during the summer, any variety can be grown at this time of year (for an extended harvest in these latitudes, sow early, mid and late . For people like me in warm-temperate latitudes, the best varieties to grow are apparently the short and intermediate day length ones. The late varieties are unsuitable for northern climbs (towards the equator, due to Australia being in the southern hemisphere and being generally a bit wonky in most things) as the onion bulbs only form once day length reaches the magic fifteen hours long.

Propagation and harvest

Bulb onions can be grown from seeds, seedlings or sets (immature bulbs that were grown the previous year). With seeds, you are bale to find the widest choice of variety.

Seeds can be sown into the ground, which is the easiest option. The seeds need to be up to 2cm deep in the soil in rows, with seeds 25-30cm apart, to allow enough room for bulb development. Seeds can be sown in trays/punnets too. When transplanting seedlings into a bigger space, avoid planting the seedlings too deeply-ensure that the roots go into the planting hole, and that the base of the bulb is just below the surface. Sets do mature more quickly, but then they do have a head start. With spring onions, sow seed thinly in rows, tinning if required when large enough to handle.

Before planting, it is advised to incorporate fertiliser into the soil and mix throughly. Avoid too much nitrogen as nitrogen encourages leafy growth over bulb production.

Bulb onions need a good 6-8 months of growing before they are ready for harvest. Keep the soil weed free and add some extra fertiliser as the bulbs start forming. The onions are ready to harvest when the leaves dry out-if they rustle, then you can take them out the ground. Cure the bulbs in sunshine for a few days, then store in a cool, dry area.

Onions can also be grown in pots, but the yield will be smaller than those grown in the ground.

Pests and disease

Onion thrips can be a problem at the base of the central leaves, made worse in dry weather. Ensure plants are well watered.

Onion maggot is a problem mainly in sandy soil, and/or when animal manure is used at planting time. Use inorganic fertiliser if there is a problem here.

Fungal diseases can be the major problem with onions. The best way to deal with this is by practicing crop rotation.

Downy mildew is fairly common in damp conditions. If severe, it can cause plant death. Improve both soil drainage and air circulation.

White rot (at the plant base) is also an onion killer. Remove plants, along with as much soil as possible, and dispose of in general waste and not the compost heap-it will cause you trouble in the future!

Uses

Onions can be used in food, both raw and cooked. They are often processed into pickles and chutney. They are apparently low in energy and a good source of Sulfur and vitamin C.

References

• Food plants of the World: Identification, Culinary Uses and Nutritional Value, 2nd Edition, 2019, Ben-Erik van Wyk, Wallingford/Boston, CABI
• The complete book of vegetables, herbs and fruit in Australia, 2016-revised and enlarged edition, Biggs, M., McVicar, J., Flowerdew, B., Simon and Schuster Pty Ltd, Cammeray
• https://www.diggers.com.au. Accessed 21/04/24