Growing Onion

Allium cepa : Amaryllidaceae / the onion family

Jan F M A M J J A S O N Dec
    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
  • 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 Mar 23, Susan (USA - Zone 6b climate)
Can I direct sow intermediate onion seeds in fall in a raised garden bed covered with leaves and over winter them. Zone 6b
29 Jan 23, Gladis (USA - Zone 10a climate)
What variety grows best in zone 10a (Southern California)?
29 Jan 23, Ron Holt (USA - Zone 7b climate)
I would like to grow onions (sets) in my garden this Feb. 23 to be harvested as mature onions in about 6 months. I would prefer sweet onions. Can you suggest a a particular type ? Do I need to buy heated onions? Thanks, Ron
19 Jan 23, Sharon Burke (USA - Zone 7b climate)
I took a kitchen scrap from a yellow onion and now I have roots what kind of soil should I plant this in for indoor in January please and thank you
24 Sep 22, digna carwell (USA - Zone 10a climate)
Hello I lived in 10A zone I would like to know when is the best time to grow , onions , garlic, carrots and mist vegetables? Thank you in advance for your response.
03 Oct 22, (USA - Zone 4b climate)
Check the planting guide for each crop.
10 Aug 22, vivian gibson (USA - Zone 9b climate)
I have texas grano onions to make set. blue lake pole beans, purple hull peas, tomato(transplant),Bell pepper (Trans plants) when do I plant? putting them in my big pots these are all going into large pots.
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 .
06 Oct 22, Melinda Schwab (USA - Zone 8a climate)
Absolutely! We do all the time! We always cut the onions we buy horizontally in half when cooking and carefully peel down to the middle chunks where you can see how many "dots" are gonna be onions next year. We have a big patch of sandy loose soil that has a lot of chicken manure and/or compost here or there that we plant all of them in. We plant them an inch or so under the soil (totally covered up is best but not too deep) and we do not break them apart first. They grow into BIG beautiful onions in a year or so if you give 'em a drink of water when its dry for weeks. AND they make seeds too! Good seeds if you let them dry all the way out! We love getting free food from cooking scraps... with a bit of pre-planning on slicing the onions right to begin with... Try replanting carrot tops if you want fresh seeds... the top 2" of a regular carrot grows into fluffy foliage and sends up nice fresh seed heads in late summer. Freebies are fun!
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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. Gardenate 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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