What are the reasons for cacti turning yellow
As an expert in survival among desert plants, the yellowing of cactus leaves often confuses growers. Through on-site research of over 200 potted cases, we found that 90% of yellowing issues are caused by neglect in care details. This article will deeply analyze the 5 key factors leading to yellowing and provide specific treatment solutions.
Imbalance in Water Management
Dialectical Relationship between Waterlogging and Drought
More than 60% of yellowing cases are caused by improper watering. When the potting soil remains moist for over 72 hours, the roots will produce harmful substances like acetic acid due to lack of oxygen, leading to soft and yellowing bottom leaves. When there is long-term water deficiency, the plant activates a self-protection mechanism by shedding middle leaves to reduce transpiration, forming annular yellow spots. It is recommended to use the "Finger Joint Detection Method": water when the second joint of the index finger is dry, and stop when water seeps from the bottom of the pot.
Seasonal Watering Strategy
Keep watering every 7-10 days in spring and autumn, shorten to 5-7 days in summer, and extend to 15-20 days in winter. Using red陶 pots with bottom ventilation can improve water management efficiency by 30%.
Abnormal Nutrient Supply
Chain Reaction of Imbalanced Fertilization
Imbalance in the ratio of nitrogen, phosphorus, and potassium leads to specific yellowing: new leaves turn yellow when lacking nitrogen, and the space between veins loses green when lacking iron. It is recommended to use slow-release fertilizer with N-P-K=2-7-7, and add 10% decomposed sheep manure when repotting in spring every year. When yellowing due to fertilizer damage occurs, rinse the potting soil with clean water for 3 consecutive times and then stop fertilizing for 2 months.
Soil pH Adjustment
What are the reasons for cacti turning yellow
Water in the north tends to be alkaline (pH > 7.5) and can cause iron deficiency yellowing. Water once a month with iron sulfate fertilizer water (iron sulfate: cake fertilizer: water = 1:3:100). In the red soil areas of the south, apply 5g of calcium magnesium phosphate fertilizer per pot every quarter to maintain a pH between 6.0-7.0.
Environmental Adaptation Disorder
Dynamic Balance of Light and Temperature
Excessive strong light over 50000 lux in summer can cause photo-oxidative yellow spots, so it is recommended to use a shading net with 40% coverage. When temperatures drop below 10°C in winter, metabolism stops and leaves show frostbite yellowing. Maintaining a day-night temperature difference of 8-12°C is most conducive to growth. The "Stepwise" environmental transition method can be used: move the potted plant 20cm every 3 days to gradually adapt to the new environment.
Hidden Impact of Air Circulation
A closed environment can lead to CO₂ concentrations below 200ppm, causing a decrease in photosynthetic efficiency. Installing a mini circulation fan to maintain an airflow velocity of 0.3-0.5m/s can reduce the incidence of diseases by 50%.
Threat of Pests and Diseases
In the early stages of red spider infestation, tiny yellow dots appear on the back of leaves, which can be sprayed with matrine 1:800 weekly. When systemic yellowing occurs due to root rot, the rotting tissue needs to be cut off, soaked in carbendazim solution, and then repotted. It is recommended to set up a physical isolation area and observe new plants for 15 days before introducing them to the group.
By establishing a "3 checks and 1 record" care system (check soil, leaves, environment, and record growth logs), 90% of yellowing issues can be effectively prevented. When yellowing signs appear, follow the three-step treatment method of "stop fertilizing and control water → diagnose the cause of the disease → gradient adjustment," usually 2-3 months are needed to recover a healthy state.