Reasons and Solutions for the Yellowing of Geranium Leaves
As a widely popular windowsill flower, geraniums captivate countless gardening enthusiasts with their vibrant colors. However, the yellowing of leaves during maintenance often causes headaches for growers. This article analyzes the three main causes from a professional perspective and provides actionable solutions to help you restore vigorous geranium plants.
Temperature Control: The Lifeline of Geranium Growth
Typical Symptoms of Temperature Imbalance
When the ambient temperature drops below 10°C, the plant initiates a self-protection mechanism by reducing the synthesis of chlorophyll in the leaves to decrease metabolic consumption. When the temperature exceeds 30°C, the root absorption function is impaired, leading to an imbalance between leaf transpiration and water supply. This dual temperature stress often causes yellow patches with crispy edges on the leaves.
Accurate Temperature Control Solutions
It is recommended to equip a digital thermometer and hygrometer for real-time monitoring. In winter, a double-layer insulation method can be used: an outer layer of transparent plastic bags (which need to be ventilated for 2 hours daily) and an inner layer of foam board placed under the pot. In summer, water can be sprinkled on the ground at noon to cool down, and using a shading net will enhance the effect.
Nutrition Management: The Art of Scientific Fertilization
Formation Mechanism of Fertilizer Burn
Excessive fertilization can cause a sharp increase in the soil EC (electrical conductivity) value. When the value exceeds 3.0mS/cm, root cells will experience plasmolysis. Especially when organic fertilizers are not fully decomposed, the ammonia produced during the decomposition process can directly burn the fine roots.
Emergency and Preventive Measures
Upon detecting fertilizer burn, an immediate three-level rinse should be performed: first, use the siphon method to remove standing water from the pot bottom, then replace the soil solution using the immersion pot method, and finally rinse the potting soil from multiple angles with a soft tube. For daily maintenance, it is recommended to follow the principle of "frequent application of light fertilization," applying diluted liquid fertilizer (2000 times) every half month during the growing season.
Light Adjustment: The Art of Balance
Light Intensity Tolerance Threshold
The optimal light intensity for geranium photosynthesis is between 20000-35000Lux. When direct sunlight exceeds 50000Lux (which can reach 100000Lux at noon in summer), the leaf stomata will remain closed, leading to photo-oxidative damage. This causes yellow-white sunburn spots on the leaf surface, accompanied by curling.
Smart Shading Solutions
It is recommended to use a 50% aluminum foil shading net, which can reflect some of the intense light while ensuring air circulation. For plants with burns, a 0.1% magnesium sulfate solution can be sprayed to promote chloroplast repair. When pruning, be sure to retain 1/3 of the damaged leaves as a transition.
Advanced Maintenance Techniques
In addition to the above three main factors, it is also necessary to note: ① Use陶盆 (clay pots) to enhance breathability, with a soil mixture of peat: perlite: vermiculite = 5:3:2; ② Rotate the pot regularly to ensure even light exposure; ③ Use bamboo vinegar solution for soil disinfection every quarter. When new leaves fully unfold and show a healthy dark green color, it indicates that the plant has resumed normal growth.
Through systematic environmental control and meticulous management, the yellowing of geranium leaves can be effectively controlled. It is recommended to establish a maintenance log, recording key data such as temperature and fertilization, to gradually master the plant's growth patterns. Remember, addressing initial yellowing symptoms promptly can prevent the entire plant's health from deteriorating.