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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
    Red onion
  • Young brown 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

08 Jul 17, thulani (South Africa - Summer rainfall climate)
Hi, i would like to plant onions in mpumalanga and my area were I live its cold mostly when its rains its pours. So can my onions grow very well in such environment?
03 Jul 17, Paris (Australia - cool/mountain climate)
I'm about to start growing onions from seeds and it says keep them under cover until early spring when they are ready to be planted out, I'm just wondering exactly what undercover means. Does it mean inside undercover or just out of direct sunlight outside. "Undercover" is very vague and I don't want to mess these up.
04 Jul 17, Liz (New Zealand - sub-tropical climate)
When we say 'undercover', we mean somewhere which will not have extremes of temperature and cool down at night. e.g on a covered deck : or in a cool greenhouse.
12 Jun 17, Margaret Shaw (Australia - temperate climate)
I have planted about 100 spring onions about 2 wks. ago, all looking good, do they benefit from any fertiliser during the growing period. I dug in a small amount of compost before planting. Thanking you, Margaret.
15 Jun 17, John (Australia - temperate climate)
Onions like a good soil but do not like too much manure/fertiliser as it will cause soft growth which will be susceptible to fungal problems.
02 Jun 17, (Australia - temperate climate)
Hello, what does it mean when the onion doesn't form a proper onion bulb but the stem becomes thick. This happened to me last year after having a good crop the year before. Cheers
07 May 17, jimmy (South Africa - Dry summer sub-tropical climate)
may sell them while they're still green?
07 May 17, (Australia - sub-tropical climate)
Hello Jimmy, We need a bit more information. Do you want to sell the onions while they are small or when they are larger, before the tops die down. You can sell or eat onions at any stage but if the tops have not died down they will not keep very long.
04 May 17, Paul (Australia - temperate climate)
How deep do you plant the onion seedling if you buy a small tray from a garden centre or Bunnings?
06 May 17, Sean (Australia - sub-tropical climate)
Onion seedlings from punnets are usually very small.Make a V shaped trench abut 50 mm (2") deep and lay them along one side of the trench at recommended spacing (probably 100 mm (4") then carefully draw the soil from the other side of the trench over the base of the seedlings. This is best done on a cool overcast day or in the evening as a warm sunny day will stress the little seedlings too much. They might stay laying down for a few days but will soon be upright.
Showing 1 - 10 of 170 comments

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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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