Kale cultivation in polytunnels G U I D E B O O K S E R I E S O N C U L T I V A T I O N
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T U N N E L
Kale = superfood Kale is a brassica plant that returned to grace, landing more regularly on domestic plates. It was cultivated during antiquity, and spread over time throughout Europe. Forgotten for ages, kale is now considered a superfood, thanks to its nutritional and health values. Added to energy drinks, appreciated by dieticians and bloggers, it disappears from vegetable shelves as soon as it is displayed.
Kale properties The plant contains a number of vitamins  (C, B1, B2, E, K, PP, A), significant amounts of micro- and macro-elements, easily assimilable protein and folic acid. In Poland, this vegetable has only recently become popular, with many people believing that other brassicas species are much tastier. Properly prepared, kale is not only tasty but also looks attractive. It is suitable for soups, salads, quiches and as a cocktail ingredient. In spring, young shoots are the first edible vegetables that can be eaten straight away. Among the benefits of the plant, its cultivation in a foil tunnel is very easy, and the vegetable is not demanding.
Kale - appearance Dark green or purple - the plant leaves form a spreading rosette. Some varieties can reach up to 90 cm with even such a diameter. In the first year of growing, thick corrugated leaves appear on solid stems, flowers and seeds appearing the second year. As it is a two-year plant, seeds are collected as the material for the next crop after emergence of inflorescences and formation of buds.
Growing requirements Kale is a plant that is easy to grow in a foil tunnel, with low growing requirements and is well suited even in unheated structures. It is exceptionally resistant to low temperatures, but it is important to protect the vegetable against drying winds. This weather factor is the biggest threat for the plant, but the foil cover will fully protect the kale from drying out. As far as the soil is concerned, the full growing potential is obtained on light, sandyclay substrates and most importantly damp.
Fertilization After spreading manure, kale is left to grow the first year on a relatively poor soil and on a more fertile soil the second year after compost enhancement. When introducing it in a foil tunnel, it is worth enriching the soil with mineral fertilizers like potassium. Carefully add nitrogen, the plant - as any other in the brassica family is sensitive to the presence of this element. Recommended doses of the individual components per 1 ha are: 150 kg N, 50-100 kg P2O5, 200-240 kg K2O, 140 kg CaO. Kale can be grown following harvest of all vegetables except brassica ones.
Cultivation methods
The best solution is to start growing from seedlings, as sowing it requires a lot of time to reach maturity and a lot of nursing work. Cultivation starts in spring, sowing in seedbed in May or the second half of June. Plant young kale to increase their resistance to the seedling death disease. When they reach a height of 15 cm, they are introduced into the garden tunnel, keeping a spacing of up to 70 cm between rows and 50 cm in lines. As already mentioned, it is a resisting plant, so any loss of seedlings is minimal.
Kale - harvest Its exceptional resistance to frost makes harvesting possible even in winter. Leaves become tastier and tenderer after thawing, so for a good taste, it is even better to harvest them after the first frosts. Avoid cool and drying winds that can lead to plant death,and to increase the viability of the plant, you can cover them in winter with straw, although such treatment is not necessary if cultivated under cover. The leaves are unfortunately unsuitable for long-term storage, kale should be collected immediately before preparation for consumption.
Pathogens and pests Brassica plants have a great deal of pest and disease hazards, while kale is more resistant to pathogens. The greatest damage is made by aphids that can destroy most of the vegetables. To prevent this, you should observe and react to any changes and illnesses. Properly adjusted dosage of treating agent will destroy habitat of pests, but identify first the kind of insect that is responsible for the attack.
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