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

13 Oct 20, Kelly (South Africa - Summer rainfall climate)
Hi there, I planted white onions in May, they have not yet yellowed and the stalks have not fallen over- we're having a lot of rain fall early on and I am afraid they will rot if I leave them in the ground while it rains so much. Can I harvest them before they have yellowed or will they still mature correctly despite the rain? Any tips or advice would be much appreciated Thanks
16 Oct 20, (South Africa - Summer rainfall climate)
It says plant seed Feb Mar and you planted May, that is the problem. Check to see how big they are, if a good size pull out. You be the judge, keep an eye on them, if they look like going rotten out they come.
13 Oct 20, Liesl Mittan (South Africa - Summer rainfall climate)
We planted onions late in march , they are ready and some are flowering .They should dry in the ground , but we are having rain. What do I do . Take them out and dry them hanging or leave in the ground and hope for hot weather . Thanks
19 Oct 20, (South Africa - Summer rainfall climate)
Pull them out.
10 Sep 20, Vicky (South Africa - Summer rainfall climate)
I planted red onion seedlings in April. I was waiting for the tops to bend over, as I've read. But now they're flowering. When should I have harvested? Also. The necks are very thick.
11 Sep 20, (South Africa - Summer rainfall climate)
I don't grow onions but it says 24-34 weeks until harvest. It is probably time to harvest if they are going to seed. Pull out and allow to dry.
01 Sep 20, M.fourie (South Africa - Summer rainfall climate)
My onions grow big but don t have any bulbs.thy were planted from seedlings juni july and grow easy but till now no bulbs.we are in south of namibia
03 Sep 20, Anonymous (South Africa - Semi-arid climate)
Work out your climate type from the Blue climate Zone tab at the top of the page. Then check the planting guide. You may have planted out of season or at the very end of the season. Usually if something grows really well but doesn't produce a crop your soil is too rich, too much nitrogen.
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.
Showing 1 - 10 of 262 comments

The onions that are big and going to seed need pulling out now. In fact any that are going to seed need pulling out now. Look up the internet for more info.

- 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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