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 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

Your comments and tips

01 Jun 16, Annie (Australia - cool/mountain climate)
In regards to soil temp for onions. You suggest 8-30 degree temps are best but my app is saying plant in garden now, (Natone, Tas) We are currently getting 2-15 degrees on average and dropping with morning frosts. Will onions survive or do they need to go into the hothouse?
26 Jun 16, stephen kettle (Australia - cool/mountain climate)
Hi Annie, I'm in Latrobe, and I've always planted onions out on , or around the shortest day
25 May 16, Colin Campbell (New Zealand - temperate climate)
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.
29 Apr 16, Daniel (Australia - temperate climate)
I'm trying an idea of planning the base of spring onions I buy at the green grocers after eating the top portion. Has any else tried this?
01 May 16, Jordan (Australia - sub-tropical climate)
Yep, works a treat. Put the bottoms in water to let them grow roots and transplant.
27 Apr 16, Noel Oliver (Australia - temperate climate)
What month to plant red onion seed and brown onion seed
30 Apr 16, Paul (Australia - arid climate)
Onions can be grown all year round and with regularly planting seed every month you will have a continuous crop. Always let the most vigourous go to seed so you have a constant supply as onion seed does not remain viable for too many years, 3 tops if you want good germination rates.
21 Apr 16, Karina (Australia - sub-tropical climate)
Hi I've planted onion seeds directly into the garden bed and then mulched over the top. Should I have waited until the seedlings grew before mulching? I've heard that like carrots you are supposed to thin them out? What should I do? TIA
30 Apr 16, Paul (Australia - arid climate)
Mulching over seed will not allow them to germinate and then push through to the sun. Onion, lettuce and carrot all grow well together (The Three Sisters) and need to "see the sun" to germinate well. I plant the three mixed together thrown over the bed and then water in stirring the top 5mm of soil in the process and then keep moist with a misting rosehead. They will then come up thicker than hairs on a cats back and effectively do not need mulch until you have thinned out the baby carrots to allow bigger ones to grow. Lettuce you can pick and let come again while the onions slowly get bigger. Trim dead and yellowing onion leaves to encourage more growth.
11 Apr 16, theresa (Australia - temperate climate)
Which variety red, white, brown onions seedlings ,when to plant as I understand they are planted at different times to minimize bolting. Thanks
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