Flower Response Measures to Persistent Cold, Rainy, and Overcast Weather

Since December of last year, the persistent cold, rainy, and overcast weather has had a significant impact on flower production in the middle and lower reaches of the Yangtze River. The flowers have shown poor nutrient accumulation, weak growth, delayed flowering, excessive elongation, leaf yellowing, incorrect flower colors, and even death due to diseases. Currently, it is the preparation period for spring greenhouse seedling and transplanting of flowers in the province. Some winter-grown lilies, last year’s overwintered African daisies, as well as foliage plants like ivy and potted plants like Kalanchoe, are all entering the market. To mitigate the adverse effects of the cold and rainy weather, the following measures are recommended:

1. Timely Drainage to Reduce Wet Damage

Timely drainage should be carried out around the greenhouse perimeter to avoid poor drainage, which could lead to rainwater seeping into the greenhouse, causing waterlogged soil and a humid, cold environment that affects root growth. The internal and surrounding drainage ditches of the greenhouse should also be cleaned regularly to ensure that there is no water accumulation.

2. Ventilation, Insulation, and Promoting Growth

Flowers in facilities, such as African daisies and lilies, should use double-layer film for insulation. When the daytime temperature exceeds 5°C and the greenhouse temperature rises above 8°C, ventilation should be carried out immediately. Ventilation should typically occur at 9 a.m., and the ventilation openings should be adjusted based on the internal temperature of the greenhouse, ensuring that cold air does not flow into the greenhouse. Ventilation time should be extended during the day but should not be too long. Generally, close the greenhouse for insulation around 4 p.m. Cold-tolerant flowers like chrysanthemums, which grow faster in spring, should have enhanced ventilation in their greenhouses.

3. Strengthen Control of Key Diseases

Key diseases such as damping-off, gray mold, blight, sclerotinia, and root rot should be effectively controlled. Smoke agents like “smoke-guard” can be used for treatment, but these should be used cautiously for African daisies and chrysanthemums, especially avoiding their use in small hoop houses to prevent phytotoxicity. Diseased leaves and rotten buds should be promptly removed from the greenhouse and disposed of outside to prevent disease spread. Pesticide spraying should be carried out on sunny mornings after the greenhouse temperature rises. For blight and downy mildew, spray with 68.75% fluopicolide and dimethomorph SC at a 1000-fold dilution, or 80% metalaxyl WP at a 1000-fold dilution, or 18.7% oxamyl-pyraclostrobin WDG at a 1000-fold dilution, every 3-5 days for 3-4 treatments. For powdery mildew, rust, and anthracnose, use a 30% tebuconazole 2000-fold solution, or 75% hexaconazole•tebuconazole WDG at a 2500-fold dilution, or 250g/litre pyraclostrobin EC at a 2000-fold dilution, spraying every 5-7 days for 3-4 applications.

4. Strengthen Chrysanthemum Seedling Management

Chrysanthemum seedlings should be grown in suspended seedbeds within large greenhouses and covered with multiple layers of film for insulation. Supplemental lighting should be used to extend daylight hours. When the nighttime temperature falls below 5°C, a three-layer film should be added for insulation on the seedbeds. After transplanting, watering should be increased appropriately, as soil moisture is crucial for survival and root growth. Once the seedlings have survived transplantation, the watering amount should be controlled to maintain proper hydration. When the nighttime temperature inside the greenhouse is above 10°C, only double-layer film insulation should be used. Daytime ventilation should be strengthened, and the maximum temperature in the greenhouse should generally be controlled between 15°C and 20°C.