How To Grow Onions


LIGHT: Full Sun – green onions tolerate partial shade
SOIL TYPE: Rich, well-drained loam
pH RANGE: 6.0 – 7.5
MOISTURE/WATERING: Keep moist, not waterlogged
KNOWN PESTS: Onion maggots



Onions grow best in rich soil that drains well. But, onions will also grow in sandy or clay soils that have been built up with organic material.

Onion seed should be planted as soon as the soil can be worked, depending on spring weather. onions can be planted until mid june – depending on your cliamte. Since onion seedlings are fairly tolerant to cold, they survive in the soil in cold weather as long as the ground does not freeze. I have found that planting onions in slightly raised rows has produced good results with nice sized bulbs.


Plant onion seed as soon as the soil can be worked in the spring. Onion seed germinates in a wide range of soil temperature, 18-29°C (65-85°F). Sow and cover onion seed with ½” of soil and keep moist. Onions cCan be started indoors 6-8 weeks prior to planting in the spring. Thin or transplant to 3-4” apart in rows 18-24” apart. To plant onion sets, simply press sets into the soil about 2” apart. Later thin to about 4-6” apart to allow bulbs to mature. Bunching onions can be left at 1-1½” apart. Space shallots 1” apart in rows 4” apart.


Onions do well with beets, cabbage family, carrot, kohlrabi, lettuce, parsnip, pepper, spinach, strawberry, tomato, turnip.


Onions benefit from full sun, a soil pH of 6.0-7.5 and a well drained soil with plenty of compost or well rotted manure added. Feed onions with a complete balanced fertilizer during the growing season, particularly when the bulbs start to form.


Bunching onions are used when young and green. To harvest storage onions: when onion tops begin to fall over, turn brown and wither, it is time to harvest. Tipping bulbs over to break some of the roots will speed drying. Pull and place onions in dry, warm airy location out of direct sun for up to 3 weeks to cure. After curing process is complete, store in cool, dry location. The drier the onions, the better they store.


Storage rot may be the result of diseases encountered during the growing season. Make sure onions are thoroughly cured before storing. Onion maggots are common and can be a serious problem. Onion maggots are the result of onion flies laying eggs on the onion plant or soil at the base of the onions. Removal of all onions and culls after the onions have been harvested leaves no food for the onion maggots to live on over the winter and early spring. Use row covers early in the growth cycle to prevent flies from depositing eggs on young stems and soil.

If you discover onion maggots, remove infected plants and discard in garbage – not in the compost or near the garden. One or two infected onion plants does not mean all is lost, but you must watch carefully and remove any plants with wilting or discoloured culls. If you catch them early enough, you may be able to save a good part of your harvest. It is a good practice to remove any onion next to an infected onion until and so on until only good onions remain (yes, you will lose a few good onions, but this is better than losing all of them) – this will help insure you do not leave infected onions in the ground allowing the onion maggots to move on and infect more of your onion crops. Before storage, inspect onions carefully for signs of rot and infestation as the maggots will continue to eat the onion resulting in storage rot. Plant onions (and garlic or related plants) in a completely different area of your garden the following season.

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