Cultivation of onions in polytunnels

Cultivation of onions in polytunnels

Onion, a two year plant from the alliaceae family, is one of the oldest crop. Its unique taste and characteristic smell are an integral part of many dishes. Onions are an indispensable ingredient or addition for various dishes, giving aroma and sublime taste. This vegetable is rich in minerals and vitamins, and has been used for many years in medicine as a prebiotic that counteracts diseases, viruses and bacteria. The glycosides contained in the plant are responsible for a significant proportion of its medicinal properties. Onions are therefore used to improve digestion and metabolism , destroying habitat of bacteria, also helping in the treatment of wounds, pharyngeal and bronchial infections.

Cultivation of onion in a foil tunnel is a simple process, providing good and abundant yield, in a shorter time than in open field . Providing of course that pests do not damage the plant during growth.

Onions are grown in sunny areas, in soils rich in nutrients. The most important factor affecting the onion yield is the quality and its reaction to the soil. Before planting, you should familiarize yourself with your soil inside the polytunnel. Onions optimally grow in soils with pH ranging from 6.5 to 7.0. If the soil has a lower pH, proper liming should regulate the pH. Carefully prepare soil for growing onion, because its requirements are very high.

  • Cultivation

The first year, the plant develops the bulb from which the onions grow. In addition, green, hollow and tubular leaves will grow above the ground. Both parts of the plant are edible, they are added to  dishes as required. The second year of growth, the vegetable releases flower shoots, rarely turning into flowers. Onions can be consumed already in the first year when fully mature .
There are three ways to grow: sowing directly into the ground, planting from seedling and growing from onion sets.

  • Sowing to the ground

To cultivate onions under cover , the soil must have high content in humus and nutrient rich. Seeds should be hardened before being introduced into the ground, so that they are protected against pathogens (diseases) and pest infestations (pests). Sowing begins in spring, already in March in the foil tunnel, while only in the first half of April in open field. Onions start growing at temperatures between 2 and 6 ° C. This enables transfer even in a non-heated greenhouse, following snow melt.

Planting too late causes the plant to grow weakly, with spongy and smaller bulbs

Seeds are sown in rows 25 cm apart, 2 to 4 cm deep. When they are emerging, shoots should be limited, leaving 5-8 per row. The optimum temperature for root growth and development is 10 to 17 ° C, and at the time of onion formation – 15 to 22 ° C.  Onions should appear up to 20 days after planting.

  • Cultivation of onion from seedling

When cultivating onion from seedling, you will obtain a better quality yield than when sowing directly into the ground. Thanks to this method, the vegetable also ripens 2 to 4 weeks earlier than in the open field cultivation. The process starts with planting seeds. Pot is filled with a mixture of peat and compost. The cycle begins in early March. Onions are introduced into the foil tunnel when minimum conditions are created. Plants are arranged in rows spaced 10 cm apart. The seedlings are then moved to the next phase, according to their stage of development. When they have 3 or 5 leaves, the plant is finally placed in the ground.

Bulbs grown from seedlings are much more resistant to storage. Have a longer shelf life and have significantly lower nutrient requirements than sown directly into the ground.

  • Cultivation from onion sets

This is a very convenient method of growing onions. Onion sets are small bulbs ready to grow. The advantage of this method is that you can pick fresh onions during the whole season and at the very end, you get a mature bulb. Onion sets are planted into the ground in March, as it is not sensitive to frost. This is the optimum method for early planting of onions. The soil should be loosened and weed free, the area previously prepared to welcome the plant under cover. In order to optimize crop, 2/3 of the vegetable must be covered by soil, planting every 8 cm.

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