Growing Onion

Allium cepa : Amaryllidaceae / the onion family

Jan F M A M J J A S O N Dec
  S                    
    P P                

(Best months for growing Onion in USA - Zone 5a regions)

  • S = Plant undercover in seed trays
  • 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

Your comments and tips

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10 Aug 19, Sam (South Africa - Summer rainfall climate)
I just planted onions that got spoiled and started to grow but now each bulb has grown into a set of seedlings. Do I pull them out and plant them separately or leave them grow as they are? Kind Regards Sam
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13 Nov 19, anon (South Africa - Summer rainfall climate)
Pull apart.
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13 Jul 20, Elizabeth (South Africa - Summer rainfall climate)
Leave them to grow. Pulling apart will break the roots. A group of onions bulbs will develop and you can harvest them together or one at a time by twisting one gently.
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01 Aug 19, Mwenya Selebi (South Africa - Humid sub-tropical climate)
Where in South Africa Gauteng can l buy red onion seedlings. l have a two hector onion field. l did direct planting of the onion and only one hector has come out well. l need seedlings that are ready for transplanting to supplement, csn you help me please. Where can l.buy seedlings in Gauteng.
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28 Jul 19, Elizah Thadius (Australia - tropical climate)
Do we have an insecticide/fungicide for bulb onion? Can anyone tell me if there is any manufactured fertilizer for bulb onion?
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29 Jul 19, (Australia - tropical climate)
Look up the internet to see if there is an insecticide/fungicide. The same as my comment for sweet potato. - learn what N P and K do for plants. Then apply that to what you are growing. They don't make different fertilisers for every kind of veggie.
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16 Jul 19, Donna (Australia - temperate climate)
I'm confused I Googled what fertilizer is required for onions and 1 search says onions don't want a lot of nitrogen and another search says onions are nitrogen hungry. ...so which is it?
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17 Jul 19, (Australia - sub-tropical climate)
All plants need some nitrogen. Now if you put a lot of N on the onions, you would have a big green plant above the onion bulb and probably little bulb. N produces leaf and plant structure. Generally if you prepare your soil with compost manures etc and let it all rot in over 6-8 weeks with watering and digging it over, and maybe add a little general fert in the process then you would not have to fert the onions again. A general fert is sufficient to grow most things - look up and learn about crop rotation also.
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24 Jun 19, Cassie (Australia - cool/mountain climate)
And make sure you plant varieties that cope with your particular climate. Many varieties dont cope well with heat and will bolt to seed
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08 Jun 19, Ben Camenzuli (Australia - sub-tropical climate)
What is it that onions do not like as they grow ?? What is they like ? How to prevent onions going to seed ???
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Showing 141 - 150 of 368 comments
See comments for all plants

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.

- Liz

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