Growing Onion

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
  • 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

06 Apr 21, Duke Rick (USA - Zone 8b climate)
What is the best time to plant Maui onion seeds in my zone?
02 Apr 21, Debbie h. (USA - Zone 9b climate)
Can you plant onions that already have a green stem coming from it? Like ones in fridge if not used fast enough .
22 Jun 21, Jayne Matzkin (USA - Zone 9b climate)
I've done it. You take the outside layers off until you reach the layers the green stem is attached to and plug it in your garden. They become a bigger version of themselves. I see this a way of not wasting that onion and tossing it.
08 Apr 21, Anon (USA - Zone 4b climate)
Put the question into google and it will explain how to do it.
28 Feb 21, Barbara Esparza (USA - Zone 9b climate)
Are there any onion sets that I can plant in Texas zone 9b that are more heat resistant?
02 Mar 21, Anonymous (Australia - sub-tropical climate)
Plants generally have a temperature range that they grow in. That is why most crops are seasonal in a district. Try planting out of that range and you could fail.
16 Feb 21, Judith c Greenleaf (USA - Zone 9b climate)
Can I plant onion sets in February or march? what sweet onion varieties do you suggest for No. Ca. marine zone 9B? Thank you.
17 Feb 21, Anonymous (USA - Zone 9b climate)
Consult the planting guide calendar and the footnote at the bottom of the page. If it says plant April and you plant Feb, the seeds/sets probably won't germinate/survive . There are reasons why it says to wait until April but take local conditions into considerations.
12 Aug 21, Carol Rose (USA - Zone 9b climate)
I found Dixondale Farms to be a great help. I ordered my onion slips form them. I had never ordered onion slips before so I was a little nervous about the process. I wasn't able to plant them when they arrived but I cared for them as per instructions and only lost a few before I could get them into my newly made raised beds. I planted sometime in early June I think and they are about 3 weeks or so form being ready. I live on the Central Coast of California and these onions look great. As a pretty new organic gardener I love to share my successes. Ck out Hollis and Nancy's homestead on YouTube. It is so helpful!!
03 Feb 21, Sky Kell (USA - Zone 7b climate)
Perennial onion that multiplies for 7b zone
Showing 1 - 10 of 17 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. 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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