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

30 Nov 21, marco (Australia - tropical climate)
hi i live on the gold coast qld .i have planted onion .rossa lunga di firenze .in late october ,early november .they are there and havent done much .we have had lots of rain here and the onions have thickened up quite a bit .i have thrown more seeds in a tray and i will plant them to see how they grow out .i might be too early yet i will let u know how it pans out !!
07 Dec 21, Anonymous (Australia - sub-tropical climate)
You are sub-tropical. Click that in SET YOUR CLIMATE ZONE. Then go to onion. You basically plant onions in autumn early winter.
22 Dec 21, marco (Australia - temperate climate)
yes you are right my onions thickened up with all the rain .yet they stalled in growth again .new seed seeded yet they are thin as well .like u said wrong time of year to grow .i will keep them in the ground to see what happens .(my first year of growing onions)
23 Oct 21, Judy (Australia - temperate climate)
My onions are starting to go to seed. Why has this happened, and what can I do about it?
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.
05 Jul 21, Jacqueline (Australia - temperate climate)
I'm interested in planting red onions, I am growing spring onions, and leeks quite successfully but know nothing about red onion planting and care. Could you please advise me. I only have a small balcony style garden.
10 Jul 21, (Australia - sub-tropical climate)
All the onion family are pretty similar to grow. Plant them similar time as spring onions and leeks. If you want more info google
08 Aug 21, anne onn (Australia - temperate climate)
telling people to google something on a plant website is just lazy. @Jacqueline, you can safely plant the red onions as if they were spring onions, just allow for more space between the plants Note: Gardenate does not advise google - we assume that is how the questioner found our site)
Showing 1 - 10 of 300 comments

We're taking a break and there will be delays processing comments over the holiday season. Happy Christmas and Happy New Year!

Kate This happened to me too the first year I planted onions. Then after reading more I found that an onion grows to reproduce. It has two choices: 1. To flower. If it does then all it’s energy will pass from its bulb to the flower. Result no onion but a nice flower. 2. To form a bulb and wait for another year. This is what happpens when you bend the tops over and tie back the flower scape so it does not grow. When this is done, the onion stops putting energy into the flower and concentrates on forming a bulb. Then you get an onion. They are quite persistent so you will need to keep the tops bent over once the leaves start to brown. So plant as normal. Then when the tops start to brown bend them over and tie back the head so as to prevent or stop the flowering.

- David

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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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