Proper watering and fertilization are essential for a successful cucumber harvest, especially given the potential harm from unpredictable weather. Understanding the nuances of cucumber care is crucial for gardeners.

Cucumbers require more frequent watering than tomatoes, particularly in greenhouse environments. Ideally, water them twice a week. If that’s not feasible, provide a thorough watering once a week, supplementing with inverted plastic bottles filled with water for a DIY drip irrigation system. Agronomist Lyudmila Shubina advises applying 7–10 liters of water to each plant root, as cucumbers are broadleaf crops that lose a significant amount of moisture.

Regular fertilization is also vital for cucumbers as they develop green mass and fruits. Although cucumbers are mostly water, the belief that only warm water should be used for irrigation is a misconception. While using settled, sun-warmed water is beneficial, cold water will not harm the plants, especially since the soil is warm. Water cucumbers at the root either early in the morning or, preferably, late in the evening. Spraying the leaves with water at least once a week, particularly in the evening, helps protect against spider mites and other pests.

Yellowing cucumber leaves can indicate several issues, requiring careful examination of the plant’s condition. Causes include the plant’s natural aging process, overheating or sunburn, nitrogen deficiency, magnesium deficiency, spider mites, and fungal diseases.

Yellow leaves near the bottom of the plant may simply be old and should be removed. Overheating can be addressed by increasing ventilation in the greenhouse and watering more frequently. Nitrogen deficiency, indicated by a loss of color in the leaves, requires feeding the plant with nitrogen-containing fertilizers. Similarly, magnesium deficiency needs to be corrected with magnesium supplements or complex fertilizers.

Spider mites, which thrive in dry greenhouse conditions, can be identified by the presence of cobwebs on the undersides of leaves. Infested leaves should be carefully removed, bagged, and discarded to prevent further spread. Regular spraying of the leaves, especially the undersides, is a preventative measure. Chemical treatments should be reserved for severe infestations, while bio-insecticides can be effective in less critical situations. Fungal diseases, indicated by spotty yellowing of the leaves, can be treated with biological products containing Bacillus subtilis.

Cucumbers need regular feeding, alternating between organic and mineral fertilizers every ten days. If complex mineral fertilizers are not available, consistent and ample application of organic matter is crucial. Shubina recommends applying at least 3 liters of fertilizer per plant, carefully at the root, half an hour to an hour after the main watering. Suitable organic fertilizers include diluted cow manure or fermented grass (1 to 10 dilution) or diluted chicken manure (1 to 25 dilution).