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 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 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

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
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.
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.
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.
10 May 21, Tony (New Zealand - temperate climate)
try spraying regularly with copper, also good for rust.
06 May 21, Anonymous (New Zealand - temperate climate)
Ring your local agricultural or agric company department about the fungus.
17 Jul 20, Elaine (New Zealand - cool/mountain climate)
I am looking for everlasting onions. Think they are called Allium Cepa Perutile. They are what I would call a a shallot and grow from a shallot.bulb only and get lots around it a bit like garlic and have leaves like spring onions and don't flower or seed. If you Google Iitoi onions in USA they look like that. I moved from Australia years ago and they had grown in my family for generations. I would love to have them again. Does anyone know where I can get a few bulbs in NZ?
30 Jul 20, Sarah (New Zealand - temperate climate)
They may be what we call a multiplying, walking onion. I sometimes have some though not at this time of year.
20 Jul 20, Mike (New Zealand - temperate climate)
I found a company Garlico in NZ, they grow and sell shallots, 3 different kinds, but not like what you and I are talking about. Mike
20 Jul 20, Mike (New Zealand - temperate climate)
I took a look at the I'iotoi onion on google, the photo of them is the closest /the same to what I grow. I have always called them shallots and so did my mother. I/we have been growing them for nearly 60 years. Keep bulbs from one year to the next to replant. The only problem is I live in Australia, near Bundaberg Qld. A lot of people call different things shallots. If you are unable to obtain any in NZ you could ring your agric department and see if I could send some to you. Ring up some of the seed selling companies in NZ to see if they have them.
Showing 1 - 10 of 31 comments

I planted onion seedlings 2 months ago. They all look healthy but I am concerned at the length of the tops--up to 30cm--which is causing some lifting of the bulb. Should I trim the tops back or leave as is? Your advice would be appreciated. Thank you.

- Colin Campbell

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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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