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Growing Onion

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

(Best months for growing Onion in New Zealand - cool/mountain regions)

S = Plant undercover in seed trays T = Plant out (transplant) seedlings P = Sow seed

  • 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 46°F and 86°F. (Show °C/cm)
  • Space plants: 2 - 4 inches apart
  • Harvest in 25-34 weeks. Allow onions to dry before storing.
  • Compatible with (can grow beside): Lemon Balm, Borage, Carrots, Beets, Silverbeet, Lettuce, Amaranth
  • Avoid growing close to: Peas, Beans
  • Red 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

14 Sep 19, petre (Australia - sub-tropical climate)
Hi, Can I buy Onion sets in Australia ?. I live in Canungra Queensland. Thanks, Peter.
16 Sep 19, Anon (Australia - sub-tropical climate)
What do you mean by sets?. I don't grow onions but I would think most people grow from seeds or seedlings.
27 Aug 19, Jessica (Australia - temperate climate)
Hi, can I still plant onion in September in Melbourne? thank you
27 Aug 19, Liz (New Zealand - sub-tropical climate)
Check here
10 Aug 19, Sam (South Africa - Summer rainfall climate)
I just planted onions that got spoiled and started to grow but now each bulb has grown into a set of seedlings. Do I pull them out and plant them separately or leave them grow as they are? Kind Regards Sam
01 Aug 19, Mwenya Selebi (South Africa - Humid sub-tropical climate)
Where in South Africa Gauteng can l buy red onion seedlings. l have a two hector onion field. l did direct planting of the onion and only one hector has come out well. l need seedlings that are ready for transplanting to supplement, csn you help me please. Where can seedlings in Gauteng.
28 Jul 19, Elizah Thadius (Australia - tropical climate)
Do we have an insecticide/fungicide for bulb onion? Can anyone tell me if there is any manufactured fertilizer for bulb onion?
29 Jul 19, (Australia - tropical climate)
Look up the internet to see if there is an insecticide/fungicide. The same as my comment for sweet potato. - learn what N P and K do for plants. Then apply that to what you are growing. They don't make different fertilisers for every kind of veggie.
16 Jul 19, Donna (Australia - temperate climate)
I'm confused I Googled what fertilizer is required for onions and 1 search says onions don't want a lot of nitrogen and another search says onions are nitrogen hungry. which is it?
17 Jul 19, (Australia - sub-tropical climate)
All plants need some nitrogen. Now if you put a lot of N on the onions, you would have a big green plant above the onion bulb and probably little bulb. N produces leaf and plant structure. Generally if you prepare your soil with compost manures etc and let it all rot in over 6-8 weeks with watering and digging it over, and maybe add a little general fert in the process then you would not have to fert the onions again. A general fert is sufficient to grow most things - look up and learn about crop rotation also.
Showing 1 - 10 of 228 comments

If you sow now you would transplant in 6-8 weeks. I think onions can handle some frost. Check on the net about this.

- Mike

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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. GardenGrow 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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