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How to Grow Onions in Irelands Vegetable Gardens

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James Kilkelly
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Joined: 30 May 2006
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Location: West of Ireland

PostPosted: Sat Dec 09, 2006 12:45 pm    Post subject: How to Grow Onions in Irelands Vegetable Gardens Reply with quote

How to Grow Onions!

Growing Onions

Onions are members of the Allium family and a popular crop for those of us who grow our own food. There are three main groups of onions: salad or spring onions, which are sown in the autumn or spring, the autumn sown varieties for early bulbs, and the early sown kinds for late keeping.

Their flavours range from mild to strong and extremely strong or real tearjerker. All parts of the plant are edible but we generally restrict ourselves to the bulb.

They can be round, oval or slender, their colour can be red, yellow, white or green. It is well documented that onions are good for our health.
Garlic, for example, has a very long folk history of use in the treatment of a wide range of diseases.

Onions are claimed to have ant-cancer properties and many believe that the evidence is stacked in this theories favour. They contain vitamin A and C, phosphorus and potassium.

As well as being beneficial for our health, alliums are also good companions for other plants in the garden. They are usually planted next to roses, carrots, beet and camomile to give them protection from disease and pests; if they are good enough for plants they can surely do a lot for us too! Therefore growing onions is immensely satisfying as they are so useful.
In cooking they are used as a condiment or seasoning; few main course dishes would taste quite as good without the addition of either onions or garlic.

Onion, photo / pic / image.

Soil Preparation

Choose an open site to allow the onions as much sunlight as they can get.
Onions do best in light, sandy, well-drained, deep loam, which has been well manured; this should be undertaken in the previous autumn. The roots need air as well as moisture therefore waterlogged soil should be avoided.

Dig in plenty of compost and manure at the rate of 1 ½ bucketfuls to the sq. yd.
For autumn sowings, do not use manure or compost; sow the seed on land where a well manured crop has recently grown.

Two weeks before sowing or planting out, apply fish manure with 10 per cent potash content at 4 oz.(120g) to the sq. yd. If you are growing the autumn sown varieties, a dressing of 4 oz. (120g) of bone meal and 2 oz. (60g) of sulphate of potash can be given in February. If the land has a low lime content add carbonate of lime as a top dressing at 5 oz. (150g) to the sq. yd. best results are gained when the soil is kept at pH 6.5 to 7.0.

Yellow-green plants characterize nitrogen deficiency, whilst phosphorous deficiency results in light green plants that mature slowly. Poor bulb formation with brown leaf tips is the result of potassium deficiency.

Spring Sowing

Two sowings or plantings are essential if you are to have a year-round supply of onions. Onions need to go in as early as possible, because a long growing season should allow the bulbs to gain good size to harvest.

The first sowing is made in March where the soil has been well raked; these can be harvested from August. Make ½-in. (12mm) deep drills 1 ft. (30cm) apart and sow thinly. An excellent companion planting is parsley as this herb helps to keep the dreaded onion fly at bay, so the parsley seeds should be sown at the same time.

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Onion Sets

Onion sets are small bulbs, which are planted in the spring as an alternative to growing from seed. They have a shorter growing season and many gardeners believe them to be easier to grow and harvest, especially in the north or wetter parts of the country. Another advantage is that they are less likely to be attacked by onion fly.

Sets can be bought in which case, choose onion sets that have been heat-treated. Many people prefer to grow onions from sets rather than from seed but there are fewer varieties to choose than if you grow your onions from seed.

If you do raise sets yourself from seed, sown them thickly in May in poor soil. Do not thin out, water occasionally but do not feed.

This will produce a crop of small bulbs not more than ½ to ¾ in.(12mm - 19mm) in diameter. Lift these in September, store in a cool, dry shed until they can be planted out the following spring.

Plant out the single bulbs at the end of March in drills 1 in. (25mm) deep and 1 ft. (30cm) apart. Space the bulbs in the drills about 6 in. (15cm) apart then cover.

You can also sow the seed in January or February under cover at a temperature of 50-59 F. (10-15 degrees C.) into onion modules. These are shallow trays with individual compartments; an indentation is made in each compartment and the seed sown into these. Sowing sets this way will allow the onions to be planted out in April.

Onion seeds, photo / pic / image.

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Autumn Sowing

Sow the seeds in September in rows 9 in. (228mm) apart. This second sowing will be ready to be harvested the following June.

Thinning out is done in early spring; those that are pulled up are used in salads. However it is far better to ensure when sowing that the seeds are sown thinly, this means that there is less likelihood of attack from onion fly.

General care

The lack of rain in mid-summer will mean that Main-crop onions will require watering. In particularly dry conditions they will need to be watered for about an hour every ten days or so. However water should not be given when the bulbs start to ripen in late summer or early autumn.

Thin out where necessary and hoe the soil regularly to keep down weeds.
Ready to use bulb onions are ready for use in late August and September or early October. Those harvested first are those, which were sown in autumn. When the tops are beginning to turn yellow, bend over the necks of the plants; the leaves will gradually dry off; when the skin of the bulbs turn yellow, lift them gently and lay them out in the sun to dry off; turn them occasionally so that they ripen evenly.

If the weather is poor, complete the ripening-off on shelves in the greenhouse or shed. After about two weeks they should be ready to put into store, during this period the flavour will develop.

Onions may be stored in boxes but to ensure that air circulates around them, make up a rack of wire netting, two or three tier high and place this in each box. Alternatively their stalks can be tied onto a rope so that they form an elongated bunch. Start by tying the first by its stalk to the rope with raffia and then continue to tie more around and above working them along the piece of rope or stout twine; these can then be hung around the shed ready for use.

Onion neck rot:

The fungus Botrytis allii causes this disease Onion neck rot. Symptoms include the development of a slightly fluffy grey fungal growth around the neck of the onion; a softening of the tissues follows; black fungus then takes hold.
This disease can be avoided by purchasing onion sets from a reputable source and by crop rotation.

Onions should not be grown on the same site for more than one or two years in succession. Onions with white bulbs are more susceptible than those with yellow or red bulbs.

Downy mildew:

Those leaves which are effected develop off-white or grey, fluffy fungal growth, start to discolour and die back. The disease is caused by the fungus Peronospora destructor and is encouraged by dampness or humidity. Remove affected leaves and rectify growing conditions.


The term bolting means that the plant has run to seed and has sent up a flower stem before reaching full maturity and is in fact quite a common problem. This is especially so when temperatures are relatively low early in the year, or if there is a late cold spell. Very hot, dry conditions may also induce bolting.

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