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 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

01 Aug 22, Caridad Pupo (USA - Zone 8b climate)
Id like to grow some granex onions like the Texas Grano. Can I sow the seeds now in seed trays and plant them outside n September? Do the onions become dormant when the weather gets cold?
15 Jul 22, carmen rodriguez (USA - Zone 8b climate)
can i grow onions from bought from store ? i cut bottom of onions put in water as soon as it starts growing roots i plant them . when should i plant them and i have not been successful im in zone b please help me .
09 Jun 22, Michael Pellerin (Canada - Zone 5a Temperate Warm Summer climate)
I Live in Miramichi, NB Canada and looking to what growing zone I am in and what type of oignions grow better, short day, intermediate or long day , or what varieties are better for my zone Thank-you
17 Jun 22, Anonymous (Canada - Zone 4b Temperate Warm Summer climate)
Go to the blue tab above and work out which zone you are. Pick what variety you want to grow.
02 Jun 22, Rick Nuffer (USA - Zone 7a climate)
do walla walla onions grow well in Utah?
18 Apr 22, Graham Bower (Australia - temperate climate)
I have been growing butternut pumpkin and trombone zucchini in close proximity and saving seed for following season. I saved seed from each for this seasons planting. This year my produce appears to be a cross of thes two . Is this possible? Can these cross pollinate? The fruit has been huge and eats very much like a quality butternut.
21 Apr 22, Anonymous (Australia - temperate climate)
I believe they do cross pollinate.
26 Mar 22, Heidi (Australia - temperate climate)
I have some onion sets left over from last year and want to plant them. All the articles I have seen thus far talk about growing them from seed/seedlings. Ours is a temperate climate, so when is a good time to plant them?
19 Apr 22, Graham (Australia - temperate climate)
Sets . Another word for seedlings. If they are still fresh and viable they should be OK. In saying that, I am surprised that they are still OK from last year. (Gardenate : 'sets' are usually small onion bulbs with brown, papery skin)
29 Mar 22, Anonymous (Australia - sub-tropical climate)
Check the top of the onion page.
Showing 1 - 10 of 313 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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