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Growing Onions - advice on how to grow Onions

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Onions are one of the most popular vegetables for growing in home gardens and are one of the first crops of spring. They can be stored over winter thus making a versatile crop

They are used in a huge range of culinary dishes, both raw and cooked.


If adding manure or composted organic matter then add a few weeks before sowing / planting out.

You can tread the soil gently to firm it up a bit prior to sowing.


Onions can be planted from seed or from sets (small partely grown onion bulbs). Sets are more expensive but they tend to be more reliable in their results and also require less work - no thinning and reduced onion fly risk.

If sowing from seed then sow in drills about 2cm deep with about 1 inch between seeds. If sowing in rows then space the rows about 30cm apart.

The soil should be moist before sowing so check the soil the day before sowing and water if the soil is dry.

If planting onion sets then they can be planted around Mid to Late March (earlier if a cloche / polytunnel is used). Again space rows about 30cm apart. Sow sets around 10cm apart as they shouldn't require any thinning. Dig a small hole for each set and place the set in neck upwards. When covered back up with soil the tip of the neck should just show through the soil surface.

Spring onions (scallion) can be sown from April and planting should be staggered every few weeks to ensure a continuous crop throughout the growing season.


Onions will grow in most cliimates and are frost resistant.

Soil type

Onions will grow in almost any soil from sandy loams to heavy clay. The soil should be firm. If your soil is heavy then you can introduce some organic compost or manure into the soil to help its moisture retaining properties.

Onions prefer a slightly acidic soil - PH 5.5-6.5 is a good PH for growing onions.


Frequently weed between the onions by shallow hoeing, onions do not trap much incoming light due to their sparse leaf forms so weeds can take full advantage of the availalle light.

If your crop has been sown from seed then you will need to thin the onions when they reach about 5 cm in height. Thin them so that they are spaced about 10cm apart.

Onions ready for harvest


Onions are ready to harvest a week after their tops have started to fall over and are yellowed.

Use a fork to lift the onions out of the ground. Take care not to damage the skins as this invites decay organisms in to attack the onion flesh.

Onions should be harvested on a sunny day, cleaned of any soil still attached to them and then placed on top of the soil where they will dry out with the help of the sun and wind.. Leave the onions out for a few days (until the tops dry out).

Remove the tops with a sharp knife about 2cm above the onion top so that decay organisms do not have direct access to the onion bulb.

Discard any onions that show signs of decay or damage as these can affect healthy onions if they are stored .

If you want to store the onions over winter then you can cure them by hanging them in a well aired place (such as from the roof of a summer house veranda). Mesh bags or strings can be used to group and hang the onions and they should hang for about 3-4 weeks.

Spring onions can be harvested when they are about 30-40cm in height and will store for up to a week in the fridge. To prepare spring onions simply remove the outer set of leaves and wash.


Onion Fly is attracted by the smell that thinning the onions releases. For this reason the method of growing from sets rather than seed is advantageous when trying to combat onion fly. Onion blast - this fungus develops on the plants foliage with a blast of speed.