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Growing Onion

Jan F M A M J J A S O N Dec
  S   T P S   T        

(Best months for growing Onion in Australia - sub-tropical regions)

S = Plant undercover in seed trays. T = Plant out (transplant) seedlings. P = Plant in the garden.

  • Easy to grow. Grow in seed trays, and plant out in 4-6 weeks. Sow seed at a depth approximately three times the diameter of the seed. Best planted at soil temperatures between 8°C and 30°C. (Show °F/in)
  • Space plants: 5 - 10 cm apart
  • Harvest in 25-34 weeks. Allow onions to dry before storing.
  • Compatible with (can grow in same bed): Lemon Balm, Borage, Carrots, Beets, Silverbeet, Lettuce, Amaranth
  • Avoid growing in same bed: Peas, Beans
  • Red onion
    Red onion
  • Young brown onion
    Young brown onion

Onions come in a range of colours and shapes and sizes. Brown :- strong flavour and pungent. Usually good keepers for storage. White :- milder but still flavoursome. Keep fairly well. Red :- Mild, suitable to use raw in salads and sandwiches. The seedlings should be allowed to gain a bit of strength before planting out - usually 4 to 6 weeks will be enough. When they are big enough to handle, you can plant out. They start off looking like blades of grass.

They don't have to be in a greenhouse (though that would be ideal), any sheltered spot will do. The idea is to guard against rapid changes of temperature, especially at night.

Onions can be bought as young plants (sets or seedlings) from garden shops/nurseries to plant straight into garden beds. Choose your variety according to your climate and the time of year as some onions will grow better in the cooler months .

Onion bulbs should sit on the surface of the soil. Do not cover. They will take six to eight months to mature. Onions are ready when the tops start to dry and fall over. Pull them and leave to dry for a few days. Store in a cool, dry airy place. Use a net bag or make a string by weaving the tops together.

Culinary hints - cooking and eating Onion

Brown onions roasted whole with other vegetables are delicious.
Red onions add colour to salads or stir-fry.

Your comments and tips

10 Jul 16, Cassie (Australia - cool/mountain climate)
So why did my onions grow well then split and sprout? They have no intention of having their tops die back. Previously I've had them go to seed and clearly avoid the whole 'tops dying back' thing too. I sow seed in late winter and plant out the seedlings in early spring. What am I doing wrong?
18 Jun 16, Christine (Australia - tropical climate)
I have onions shooting in the vegie bin. My son said when I plant them I have to put the new growth above the soil, but I though this was the root. Which way do I plant them please?
01 Jul 16, Barb (Australia - temperate climate)
Your son is right - the green shoots are the stems/leaves starting to grow. So plant these uppermost. I find the ones that I grow from shooting onions may not bulb up properly. but they make great spring onions, and if left will divide so you'll have a little patch of spring onions.
01 Jun 16, Annie (Australia - cool/mountain climate)
In regards to soil temp for onions. You suggest 8-30 degree temps are best but my app is saying plant in garden now, (Natone, Tas) We are currently getting 2-15 degrees on average and dropping with morning frosts. Will onions survive or do they need to go into the hothouse?
26 Jun 16, stephen kettle (Australia - cool/mountain climate)
Hi Annie, I'm in Latrobe, and I've always planted onions out on , or around the shortest day
29 Apr 16, Daniel (Australia - temperate climate)
I'm trying an idea of planning the base of spring onions I buy at the green grocers after eating the top portion. Has any else tried this?
01 May 16, Jordan (Australia - sub-tropical climate)
Yep, works a treat. Put the bottoms in water to let them grow roots and transplant.
27 Apr 16, Noel Oliver (Australia - temperate climate)
What month to plant red onion seed and brown onion seed
30 Apr 16, Paul (Australia - arid climate)
Onions can be grown all year round and with regularly planting seed every month you will have a continuous crop. Always let the most vigourous go to seed so you have a constant supply as onion seed does not remain viable for too many years, 3 tops if you want good germination rates.
21 Apr 16, Karina (Australia - sub-tropical climate)
Hi I've planted onion seeds directly into the garden bed and then mulched over the top. Should I have waited until the seedlings grew before mulching? I've heard that like carrots you are supposed to thin them out? What should I do? TIA
Showing 1 - 10 of 90 comments

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This planting guide is a general reference intended for home gardeners. We recommend that you take into account your local conditions in making planting decisions. Gardenate is not a farming or commercial advisory service. For specific advice, please contact your local plant suppliers, gardening groups, or agricultural department. The information on this site is presented in good faith, but we take no responsibility as to the accuracy of the information provided.
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