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Growing Onions in Western Australia

Introducing Onions

This well know vegetable is a staple in most kitchens. Its surprisingly easy to grow at home. Onions like a cool, wet growing period to establish themselves and then produce their bulbs during the hot summer weather. They do exceptionally well in the Western Australian climate, you just need to be sure to keep them well-watered until their bulbs are formed. Plant them in autumn, so that they can make the most of the cool, wet winter weather. Onions can be harvested and used right through the growing season, first as spring onions and later as onion bulbs. If you want to store your onions, then you need to leave them in the ground and only harvest once the leaves start to fall over.

Classic Mistakes

Onions must be planted from seed, seedlings or sets. Planting an onion that has started sprouting in your kitchen is a great way to grow green onions or onion seed, but you won’t get any onion bulbs from it.


Grow in: Full Sun

Soil Preparation

Work some lime into your soil, as onions prefer a slight alkaline soil. Grow them in a bed where some heavy feeders were grown previously. Onions don’t like too much nitrogen, but they do like a soil that is full or organic matter, so work in lots of compost before planting.

Sowing Seed

Sow seed: April-May
Sowing depth: Sprinkle seeds gently onto the soil and cover lightly.

Sow seeds every 4 weeks to prolong the harvest.

Sprinkle seeds gently onto the soil and cover lightly. Once they are established, they will need to be thinned according to the spacing guidelines found on the seed packet. Alternatively, let them grow a little bigger before thinning and then used the plants you remove as spring onions.


Plant seedlings: May-June

Try to plant bought seedlings as soon as possible after you get them home and remember to give them a good, deep watering to help them settle in. When you plant your seedlings out, add a small amount of organic bone-meal to each hole. Bone-meal gives seedlings a great start and helps them to develop strong root systems which support a healthy plant. Don’t worry if your seedlings look a little sad and flop over after being planted out. Just keep them well watered and they’ll be standing up happily in a day or two.


Weed well between the onions. They don't like to compete for food and water.


When the seedlings are young, water regularly. Once they start nearing maturity, allow the soil to dry out between watering sessions. Your onions should reach this stage at some point in spring or summer (depending on the variety and when they were planted). At this point, the rains should be over, which will make it easier to control how much water they receive.


You don’t want to overfeed onions. Too much nitrogen will cause them to have lovely big leaves and underdeveloped root bulbs. Feed every three months with an organic low-nitrogen fertilizer.


Don’t mulch onions. Towards the end of their growing season, the soil needs to be allowed to dry out or they may rot.


Harvest: 25 to 34 Weeks After Planting

Onions can be harvested as soon as they reach a size you’re happy with. You will know your onions are ready to be harvested for storage when the leaves dry out and fall over. Gently dig the bulbs up and remove them from the soil. Leave them in a sunny, well-ventilated spot to cure for up to two weeks. You’ll know they’re finished curing once the skin is papery, and the roots and leaves are dry. Once they are cured, brush the dirt off them and remove the dead stems, leaves and roots. Alternatively, keep the leaves on and plait them to hang for storage. Onions should be stored in a cool, dry, well ventilated spot and kept away from direct sunlight. Don’t store any onions that are damaged or mouldy, rather use them up first before they spoil.

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