In greenhouses, cucumbers are grown in soil improved with peat substrate, or in formed beds with peat substrate, as well as in cylinders and containers filled with peat substrate. The best substrate to use is a versatile peat substrate for a wide range of vegetables and flowers and for improving the soil, made according to a special recipe from clean peat with a medium peat fraction, with the right macro- and trace element content (pH 5.8-6.5; EC 1.6-1.9 mS/cm), and with the right quantity of additives. A peat substrate for vegetables made according to a special recipe from organic peat with a medium peat fraction, with the required macro- and trace element content (pH 5.8-6.2; EC 1.7-2.2 mS/cm) is also suitable for use. Before planting the seedlings, the substrate must be aerated and additionally moistened.
Cucumber seedlings planted in the greenhouse should be about 25-30 cm tall with 5-6 leaves and a welldeveloped root system. The plants are planted at a density of 2.5-2.8 plants/m2, leaving aisles. The optimum soil temperature in the root zone of the plants should be between 18 and 20 °C. If the soil cannot be warmed to at least 16 °C, it is better not to plant cucumbers and to wait for the weather to warm up. The seedlings should be planted deeper than they were in the nursery.
Growing cucumbers in soil improved with peat substrate or in peat-only substrate can lead to the plants becoming infected with diseases and pests after a few years. The old substrate should be replaced with new substrate.
Growing vegetables in polythene packs (cylinders) or containers (plastic boxes) with peat substrate is much more cost-effective, as less peat substrate is used than if grown in the soil. Each year the plants are planted in a new peat substrate, which gives them much better growing conditions and results in much healthier growth.
After 4-5 days, the plants are tied to wires stretched at a height of 1.8-2.0 m. During the growing season, all suckers, flowers and buds must be cut from the main stem to a height of 60 cm in order to form a full plant with a strong root system. Once the plants have outgrown the top wire, 2-3 suckers are lowered down (umbrella formation).
Cucumbers are heat-tolerant plants and do not like sudden temperature fluctuations. The most favourable temperatures for cucumbers are 22-28 °C during the day and 18-20 °C at night, with a relative humidity of 80-90%. In summer, when the air in the greenhouse becomes very hot, the paths and gaps between beds are watered, but without watering the plants.
Before flowering, cucumbers should be watered infrequently but abundantly. They then grow less but produce more flowers. Once they have flowered and started to set fruit, water frequently but less. Cucumbers at maturity should be watered with plenty of warm water (22-25 °C) in the first half of the day, taking care not to splash the leaves.
After planting cucumber seedlings, it is recommended to apply a 0.2% solution of Ruter AA. Ruter AA increases the stress tolerance of the plant and promotes root formation. Cucumbers are very fast-growing and produce large yields in a relatively short period of time, which is why they need a lot of nutrients. Before harvesting, cucumbers are given a 0.2 % solution of Nutricomplex (14-11-25) and 0.1% calcium nitrate solution and at harvest Nutricomplex (6-10-32 or 6-14-30) and 0.1% calcium nitrate solution. On cloudy days and when the sun is not shining, it is recommended to apply a 0.2% Boramin calcium solution to cucumbers, which promotes the formation of floral buds. The EC (salt concentration of the solution) should not exceed 2.5. The acidity of the water is corrected with Spray Plus. Cucumbers are affected by spider mites and thrips in greenhouses with high temperatures and low humidity. The plants should be sprayed with a solution of Vertimec 0.3% and Nimazal 0.5%. Cucumbers turn yellow and suffer from false powdery mildew when humidity and temperature fluctuate. As a prophylactic measure, it is recommended to spray the plants with Previcur 0.25%.
During growth, it is necessary to control the build-up of excessive salts in the peat substrate and not to overuse nitrogen fertiliser. Diseased plants that are already dying must be removed.