Flower topping is a common physiological issue in greenhouse cucumber cultivation during winter. It can occur throughout the growing season, but it is most damaging before fruit set, significantly affecting yield and economic value. This phenomenon affects all plants in the greenhouse, from individual plants to entire fields. The causes are varied, often related to plant health and nutrient balance. Weak plants tend to flower more, while vigorous ones are less prone to this issue. Below are the main reasons and preventive measures.
**1. Seedling Stage**
During the early growth phase, several factors can lead to flower topping. First, if the nutrient soil has too much fertilizer, it can burn the roots. Second, insufficient nutrients in the soil may not support healthy seedling development. Third, if seedlings are left too long without proper feeding, they become weak and prone to flowering. To prevent this, use properly balanced soil, control seedling age (30–40 days), and ensure timely watering and fertilization.
**2. Slow Growth Period**
After planting, flower topping often occurs due to improper variety selection, excessive or unripe organic fertilizers, high temperatures, and delayed watering. Varieties with low cold and light tolerance should be avoided. Soil preparation must be done at least 10 days before planting, using well-decomposed manure and balanced fertilizers. Adequate moisture should be maintained, and water should be applied promptly after transplanting to help roots establish.
**3. Early Fruit Stage**
During the initial fruiting period, inadequate irrigation and fertilization can cause competition between vegetative and reproductive growth, leading to flower topping. Delayed harvesting also leads to nutrient depletion and physiological stress. Timely watering and fertilization, along with prompt harvesting when fruits reach marketable size, are essential to avoid this issue.
**4. Mid-Season Period**
In colder months, especially in northern China, temperature fluctuations can trigger flower topping. Greenhouses often struggle to maintain stable temperatures, with daytime highs reaching 30°C and nighttime lows dropping below 10°C. This instability slows plant growth and promotes flowering. Farmers should implement insulation measures, manage fruit thinning appropriately, and follow pesticide instructions strictly. Optimal conditions include 7.5–9 hours of sunlight, night temperatures between 11–14°C, and day temperatures around 25–28°C. A ratio of 4–7 leaves per fruit helps reduce the risk of flower topping.
**5. Late Season**
As the season progresses, plants require more water and nutrients for rapid growth. However, some farmers focus only on fruit production, neglecting vine management. This leads to nutrient shortages, aging plants, and increased flowering. Regular irrigation every 5 days, with at least 10 tons of water per acre, and application of 60–100 kg of compound fertilizer per acre, ensures sustained growth and reduces the likelihood of flower topping.
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