Onions have been cultivated as a food for about 5000 years and gathered as a remedial plant and food for longer.
It is thought by botanists that the onion originated in Central Asia where it developed its searching root system.
Although onions still have remedial properties they are grown mainly as a food source. They may be eaten fresh (leaves and bulbs) or harvested or stored. The clever grower can be eating home grown onions all year round.
Onions are not particular as to the soils they grow in but good drainage is paramount. A soil with a high pH and high in potassium suits them well. A previously manured bed is adequate. Over dressing with fertiliser may grow a larger bulb but they will not store well, soft growth will be evident and they will be prone to diseases such as white rot and botrytis and insect attack such as onion fly and thrips.
Onions have been bred to grow to many colours, shapes, sizes and various seed catalogues should be viewed to obtain what is required. If growing for an exhibition then certain top exhibitions should be contacted for seed or plants. Both culinary and exhibition onions may be grown from seeds, sets of pips.
Growing from Seed Seed may be sown in drills or stations where they are to grow. This method is mainly for autumn swings for over wintering or salad onions (scallions)
Main crop swings would usually be made in the greenhouse early in the years. The seed should be dusted or soaked in a fungicide if not already treated, and sown in fresh seed compost. Some growers cover the seed with “Perlite” or “Vermiculite” for best germination, at a temperature of 60 / 65 degrees. Seeds may be sown in a seed tray and then pricked out into pots, or sown in modules (plug trays) at 2 / 3 seeds each. They can be thinned out to one seedling or left at 2 or 3 to grow on for a higher final yield. Potting on of individual plants and growing on will result in larger individual specimens. Recommended varieties: Hysam, Tasco, Marco and Bristol.
Feed with Chempak No 8
Growing from Sets Onion sets have been produced for the commercial or amateur grower for ease of cultivation. These are plants which be been harvested early in their growth and given a period of heat treatment to prevent boiling, when growth commences after planting. They resemble small onions and are planted later to avoid the ravages of the onion fly which is troublesome in certain areas. They have been bred to produce a long storage onion of approximately 250 Gms, ideal for the kitchen, as a utility onion.
Onion sets for the kitchen are planted directly into the bed during March / April for the summer types and early autumn for the Japanese over wintering types, spacing 15cm apart approximately. Prior to planting the bed may be covered with a sheet of black polythene. Then slots are made with a penknife at the spacing distances and the sets are pushed through into the soil. The advantages of this method are: - no weeding, no feeding, no hoeing and watering as an any rain will run through the slots. During drought years watering is by capillary action.
When harvesting onions the necks should never be bent over but should be allowed to fall naturally and dry off otherwise they will not store unsuccessfully. Any onions that do throw up a seed head should be removed and eaten whilst still tender.
Any sets left over from planting can be planted at approximately 3cm apart in a box or trough in the greenhouse. These plants can be used as spring onions in salads and pulled as required. Recommended varieties: Turon, Setton, Hyduro and Marimba.
Growing from Pips This is vegetable propagation and used mainly by exhibitors. Selected bulbs of good shape and colour are set up as for seed. The seed pipes are supported as they grow up and as soon as the flowers can be seen they are cut off to leave an empty umbel centre. After a few weeks “pips” appear much like leek “pips”. These grow until they start to push each other off. These “pips” are collected individually or on the heads and are stored until planting time. They resemble small onion sets and are planted in the greenhouse in small pots alongside the seed onions and grown on in the same conditions for planting out.
The advantages to the exhibitor are that the mother bulb characteristics are reproduced with almost 100% accuracy.
Growing for Exhibition Whether growing the large quality type onions or the giant sizes, seed must be obtained for one or the other. It is doubtful that the quality bulbs will make a giant size or that the giant size bulb will compete for quality.
Seed or “pips” would be started in the warm greenhouse during December. Because winter days are short and of low light level artificial lighting is used. Whether using fluorescent tubes, high pressure sodium or metal halide the light spectrum must be high in blue light in order to maximise the plant size and gain a head start on the competition a period of 24 hour lighting is required for six weeks. This is known to be safe with regard to bolting and plants grow rapidly under this light.
Care should be taken that the light density and day length is no greater than at planting time unless the lamps are going to be used over the growing bed. The heat generated by the lamps could be a problem unless the area is well ventilated.
The plants are grown on at 60 / 65 degrees under the lights; supplementary lighting from 6:30am to 6:30pm will enhance the size of the plants up to around the middle of March .
The bed maybe pre-heated to around 60 degrees with heating cables prior to planting. If electricity is unavailable then the grower must wait until April before planting when the beds should have warmed up naturally. Planting into soils at less than 50 degrees may result in a check and cause the plants to bolt. The leaves must be supported thoroughly throughout their lives and sprayed regularly with a fungicide where disease has been a problem in the past.
It must be remembered that to obtain the best ripened skins a period of 4 to 6 weeks should be allowed from harvesting to show bench. For the giant types the freshness of the leaves must be a priority up to the end so shading may be required in late summer.
Onions may be grown on the same bed without rotation providing that no serious disease is evident. As regular amounts of organic matter are added the fertility builds up. Also a microscopic fungus called Mycorrhiza develops and grows. It should always be remembered that any sterilisation of an onion bed may kill of this beneficial Mycorrhiza along with beneficial bacteria. Recommended varieties: Kelsae and Alisa Craig.
Onions 250 Grms The Onions which the majority of gardeners grow known botanically as Allium Cepa, a biennial, which is grown as an annual for the edible bulb, namely the onion.
Like all the onion family, the 125grm onion requires an open sunny, well drained site to obtain the best results. The onion bed / site should have been winter dug, incorporating farm yard manure / compost and have a pH level of at least 6.5.
When preparing the bed / site before planting it is beneficial to apply to the ground, by equal parts by weight, Sulphate of Potash and Super Phosphate or Lime, at a rate of 113g (4 oz) per square metre (yard).
There are numerous varieties of 250 grm onion seed on the market, but one of the most popular over the past number of years has been a variety called Tasco. This variety can be sown August / September time and over wintered or sown in the traditional manner in January. The seeds can be sown mid to late January under glass with gentle bottom heat. They can be sown in trays or individual cells and then potted on as the plants develop, before planting out in their final positions in early May.
Ensure that during the early stages and throughout the growing season that the onion plants are staked to enable them to grow straight, to avoid “swan knecks” (bending), rendering the useless for exhibition purposes.
When planted out into the final positions, regular hoeing, weeding and watering in dry spells will pay dividends. It will also be beneficial, when the plants have got established and growing away, to give them a feed of nitro Chalk, to encourage the left growth. This may be applied twice, but before the beginning of July. After July a dressing of a high Potash fertiliser will help the bulbs to swell and ripen.
Once the bulbs start to swell, if growing for exhibition, it is important to check the circumference on a regular basis, to ensure that they do not grow oversize, and at the same time remove the split skins down to a whole one.
As a general rule, once the onion reaches ten and a quarter inches in circumference, then it requires lifting as this is the optimum size that will give you a 250grm specimen. Once lifted, immediately remove the roots and green blades, leaving about three inches (8cm) of blade above the onion, wash and dry, and then give a liberal dusting of Johnson’s baby powder which should be well rubbed into the skin of the onion. This helps to obtain a golden finish to the skin.
There are numerous ways in which the onions can then be stored until they are ready for the show bench. They can be placed in a box of saw dust; others prefer to wrap them before leaving them in a warm and airy place to ripen. It is really a matter of the individuals own preference.