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Growing Onions in The Northern Territory

Introducing Onions

This well-known vegetable is a staple in most kitchens. They can be a bit tricky to grow in the hot, humid Top End climate. Onions need a long, cool growing season, so be sure to plant them right at the beginning of the dry season. They 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. Onions are classified by colour and also by how many hours of daylight they need. In The Top End, only short day varieties can be grown. Heavy rains during the wet season can cause your onions to rot. Grow them in pots or raised beds to help with drainage. If you struggle to get onions growing well, spring onions and shallots might be a better option for The Top End climate.

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.

Sunlight

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 of organic matter, so work in lots of compost before planting.

Sowing Seed

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

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.

Planting

Plant seedlings: June-July

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.

Care

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

Watering

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 during the wet season. If possible, try to shield your onions from rain while the bulbs mature.

Feeding

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.

Mulching

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

Harvesting

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.

What to do about Downy mildew?

Pale leaf tips with grey mould which can turn yellow and purple is Downy Mildew. Burn all affected plants immediately.

What to do about Powdery Mildew?

Milk spray or baking soda solution work well and can be sprayed on affected plants.
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