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Growing Onion

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

(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

05 Mar 19, Carole (New Zealand - cool/mountain climate)
When is the best time to plant red onion seeds and what sort of fertilizer should I use do u use lime?
06 Mar 19, mike (New Zealand - cool/mountain climate)
Best time to plant - read the top of the page. Fertiliser - one with not a high N content. Lime - read up about using lime.
13 Feb 19, robert samuel walker (New Zealand - temperate climate)
when is the best time to put in red onion in christchurch
14 Feb 19, mike (New Zealand - temperate climate)
You have worked out your temperate - looking under onions - it is in the calendar months near the top of the page.
12 Nov 18, John (New Zealand - temperate climate)
My onions growing in Napier are sprouting seed heads. Some are large seeming perhaps fully grown or close but some aren�t. Should I nip the heads and leave them or pull them immediately?
13 Nov 18, Mike (New Zealand - temperate climate)
The onions that are big and going to seed need pulling out now. In fact any that are going to seed need pulling out now. Look up the internet for more info.
02 Mar 18, Leigh (New Zealand - temperate climate)
Hi, I’m having fun growing potatoes, Kumara and even sweetcorn that have sprouted in the bottom of my pantry. Wondering if the same should work with a brown onion that has sprouted greens out of the top?
22 Feb 18, Trevor Smith (New Zealand - temperate climate)
If I was to sow seeds in February and plant out in say May would frosts have any adverse effect on them?
22 May 19, Mark Taylor (New Zealand - temperate climate)
Onions are hardy plants and so frost tolerant, they will survive the winter. My understanding is If you plant them in Autumn you can harvest them in spring as spring onions but you won't get bulbs. They need to be planted in the spring for them to develop into onion bulbs. This is because bulb formation only starts after the summer equinox when the days start to shorten.
26 Feb 18, Mike (New Zealand - temperate climate)
If you sow now you would transplant in 6-8 weeks. I think onions can handle some frost. Check on the net about this.
Showing 1 - 10 of 18 comments

Hi, can I still plant onion in September in Melbourne? thank you

- Jessica

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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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