Growing Onion

Allium cepa : Amaryllidaceae / the onion family

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

(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

Post a comment or question Display Newest first | Oldest first, Show comments for New Zealand | for all countries
09 Dec 23, Gill (New Zealand - temperate climate)
How much watering do onions like. On tank water so hoping not heavy drinkers
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14 Dec 23, (New Zealand - sub-tropical climate)
Just give a watering 2-3 times a week depending on how hot it is.
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20 Jun 23, Sue (New Zealand - temperate climate)
My onions got a rusty fungus on the last year how do I guard against this happening again. I grew the multiplying onions found them in the garden centre as Welsh Onions. They were great until they developed the fungus.
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24 Jun 23, jim (New Zealand - temperate climate)
Copper copper copper I had same problem last year onions,garlic and leeks sometimes gardening is a pain but I still do it ??? Remember to use a sticker "sprayfix" by yates is one but most garden chemical people do similar it helps to break down the surface tension so the spray does not just run off do it before it appears and repeat it several times during the season only problem with it raining constantly it's hard to do right now. P.S. my mum used to grow welsh onions in the UK when I was a boy never saw enything like rust ?
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10 Oct 21, jim (New Zealand - temperate climate)
I am interested in planting dates for onions all my seed packets put planting in late autum winter but they are differen on this site.My father always planted onion sets are they available in NZ
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13 Oct 21, Anon (New Zealand - temperate climate)
The guide here is only a guide subject to your local conditions. You could try planting now.
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11 Oct 21, Sassy (USA - Zone 9b climate)
Jim, you just missed the spring planting season, ending in September. You can sow seed starts, in doors, under grow lights, in February to transplant in April or direct sow in May. The spring planting season begins with sowing starts in Jun, transplanting in August, or direct sowing in September. You can find this information in the Vegetable and Herb tab, click on Onion, select your Climate Zone and look at the coded calendar. Good luck with your onions next Fall.
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02 May 21, Michele (New Zealand - cool/mountain climate)
I seem to have gotten white rot/fungus tha affects most onion varieties except spring onions- they will get it but very late on...does anyone know of a vigorous type of ordinary brown or red onion that might stave it off until I can harvest? Thanks.
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10 May 21, Tony (New Zealand - temperate climate)
try spraying regularly with copper, also good for rust.
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06 May 21, Anonymous (New Zealand - temperate climate)
Ring your local agricultural or agric company department about the fungus.
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Showing 1 - 10 of 35 comments
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I was wondering if it is too late to plant onions now in Canberra. I believe day length is the key but not sure which ones are which. Any assistance appreciated. PS. I have never grown onions before.

- Evelyn

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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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