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

15 Jun 25, Jen (Australia - cool/mountain climate)
I cannot find Potato Onions on this website....as I am not successful with growing regular onions, from a seed tape, I was gifted some potato onions,.. telling me they are easy grow and keep well too>>>> Is there a organic grower who can give me some tips>>> for Tasmania as I read to plant out from now on over the next 3 mths>> Thats all???? Thanks Jen
25 Jun 25, (Australia - sub-tropical climate)
Grow them similar to how you grow onions. I tried growing somethings from tape - useless idea, I think.
19 May 25, Jan (Australia - sub-tropical climate)
Last year I planted brown onions. As they grew their stems became thick and most were as large as a softball or bigger. I kept them growing, waiting for the leaves to die back but they never did and some went to seed. I eventually bent the stems to try to dry them, but that was a bit unsuccessful and on storing them using the hanging plait method, quite a few eventually rotted. This year my onions are growing quite well, some a bit bigger than golf balls now, so what can I do to prevent the same thing from happening as last year.
25 Jun 25, (Australia - sub-tropical climate)
When they get to the size you want them, pull them out. Leave in the sun for a week or more for the leaves to dry and for a dry skin to form on the outside of the onion, then plait them. Or let them dry out a bit and store in a cool dry place - don't stack them on top of each other - let the air move around them.
04 May 25, elaine (Canada - Zone 2b Sub-Arctic climate)
can i mulch onions... i put chili powder on ground to keep out worms but im told sulfer will work
31 Mar 25, sally davis (USA - Zone 5b climate)
Can I plant onion SETS outside now? Not seeds
12 Jan 25, Hubertpenny (USA - Zone 3b climate)
Can I grown texas sweet oinon
02 Jan 25, Estelle (South Africa - Semi-arid climate)
Good. Day.. I just planted my onion seeds out.im a beginner.Just Want to know so it will be ready by what month..tx
08 Jan 25, (South Africa - Semi-arid climate)
Read the notes here - it tells you this kind of information.
13 Dec 24, Gardener (South Africa - Summer rainfall climate)
The unions is small when it's ready to harvest
Showing 1 - 10 of 383 comments

Hi, it means to take the seedlings you've grown from seed, and plant them in the ground or bigger pots.

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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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