Reasons for the Drooping Leaves of Catharanthus Roseus
As an ornamental plant that blooms throughout the year, Catharanthus roseus is highly favored for its bright and droplet-like leaves and flowers. However, during the maintenance process, it often exhibits leaves that curl downward, which not only affects its ornamental value but also indicates potential health issues in the plant. This article will systematically analyze the causes of leaf curling in Catharanthus roseus and provide scientific solutions.
I. Environmental Factors Causing Leaf Curling
1. Low Temperature Injury
Catharanthus roseus is native to tropical regions and thrives best at temperatures of 18-25°C. When the ambient temperature drops below 10°C, changes in cell membrane permeability occur, causing the mesophyll cells to contract and resulting in leaf curling. It is especially important to pay attention to day-night temperature differences in winter, as sudden drops in nighttime temperatures are the main cause of frostbite.
2. Imbalance in Light Exposure
A daily light exposure of more than 6 hours is required. Insufficient light can lead to a reduction in photosynthetic products, causing leaves to curl inward due to insufficient energy. However, when direct sunlight exceeds 40,000 lux in summer, the high leaf surface temperature can also trigger protective curling.
II. Improper Maintenance Causing Leaf Curling
1. Stress Response to Environmental Changes
When repotting or sudden environmental changes occur, the plant will produce a stress response. During this time, the stomata close, transpiration is reduced, and the leaves curl to minimize water loss, usually recovering within 2-3 weeks.
2. Mismanagement of Water
When the soil moisture content falls below 30%, the roots cannot absorb water normally, leading to physiological leaf curling. However, waterlogging for more than 24 hours can cause root rot and pathological curling. It is recommended to use the finger insertion method to check soil moisture.
III. Scientific Prevention and Control of Leaf Curling
1. Temperature Control Strategy
In winter, use double-layer protection: set up a transparent plastic greenhouse on the outside and hang LED supplemental lights 20cm away from the plants on the inside to form a 6-8°C temperature protection layer. It is recommended to use smart temperature control equipment to maintain a constant temperature of 15°C.
2. Optimization of Light Exposure
Install a light meter for real-time monitoring, provide full sunlight in spring and autumn, shade 30%-50% between 10:00-15:00 in summer, and extend supplemental lighting to 10 hours in winter. It is recommended to use full-spectrum plant growth lights, with the optimal distance being 40cm from the leaf surface.
3. Scientific Repotting Techniques
Stop watering 3 days before repotting and retain 1/3 of the original soil to protect the roots. After repotting, place the plant in a scattered light environment and spray a 0.1% seaweed acid solution to promote root recovery, then gradually increase the light intensity after 7 days.
By precisely controlling temperature and humidity, scientifically adjusting light exposure, and standardizing the repotting process, the leaf curling in Catharanthus roseus can be effectively prevented and improved. Regularly observe the plant's condition and it is recommended to apply slow-release fertilizer containing calcium and magnesium elements every quarter to enhance leaf resistance, keeping Catharanthus roseus in the best ornamental state.