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

01 Feb 08, Matt (Unknown climate)
Hi there Im a development Horticulturalist with Fairfield city council, I just wanted to find out what types of onion are transplanted from seedling. The reson i ask is i have only ever heard of direct sowing of onion seed and transplanting is very unsucessfull (especially in your common spanish, white and brown varieties).
04 Feb 08, Liz (Unknown climate)
Onions can be raised in seed trays or punnets and transplanted when about 10-15cm tall. They should be planted with just the roots covered. If sown direct, the emerging plants may need thinning. I have been successful with both methods for brown and red onions and with spring onions from seedlings.
08 Feb 08, Bryan (Unknown climate)
Onions can be successfully planted as seedlings.Grow in trays transplant at about 15cm.Before transplanting trim tops and roots by about one third, dig shallow depression, lay plants with roots only in depression and cover roots with soil. Important to select correct onions for time of year(see packet)
07 Sep 08, Jaci (Australia - temperate climate)
I am only just beginning to grow onion this year. I have heard that onion seed doesn't have a long life. Can you begin the seed's life by chitting? When harvested, how long does it need to be hung and dried for before it can be eaten. Also, how long will it keep for (if hung in the dark and kept dry)?
08 Sep 08, Ciara (Australia - temperate climate)
I just have a balcony so I'm using pots to grow a few things, I was wondering how deep a pot needs to be for onions.
15 Sep 08, barney (Australia - tropical climate)
i grow onions in winton... they are yummy =] i put horse manure on them and it works goodies :)
03 Nov 08, Alex (Australia - temperate climate)
My onion looks like this: It's about the size of a commercial onion - do I need to leave it to mature or ripen, or is it ready to pull out and eat? Thanks
03 Nov 08, Chris (Australia - sub-tropical climate)
Alex, you can pick onions at any size to use right away, so you could use yours now. To keep onions they should harvested after the tops have fallen down and dried out.
15 Dec 08, mark (Australia - temperate climate)
please help,can someone please tell me the correct procedure for drying/storing onions.thankyou and merry xmas to all.
18 Dec 08, Steve (Australia - temperate climate)
Some of my creamgold and red onions are shooting to seed. Some have large healthy bulbs. Should I harvest them now?? Others have virtually no bulb. Can I cut the seed head off and let them continue to develop?
Showing 1 - 10 of 365 comments

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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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