What to Do When a Cactus Turns Yellow
Cacti, as widely popular "lazy" plants, often cause confusion when they turn yellow. This article systematically analyzes the four main reasons for cactus yellowing, and through precise diagnosis combined with scientific care, it helps you quickly rescue your beloved desert精灵.
Root Rot Due to Overwatering
Judgment of Waterlogging Damage
When the epidermis of the cactus exudes sticky fluid and the base shows signs of softening, it is necessary to check the roots immediately. Overwatering leads to prolonged soaking of the roots, causing fungal infections and cell necrosis, forming a water-soaked rotting lesion.
Phased Treatment Plan
Mild rot (＜1/3): Use a sterilized knife to remove the diseased tissue, apply carbendazim powder to the wound, and after air-drying the roots for 3-5 days in a well-ventilated and shady place, replant in granular soil. Severe rot (＞1/3): Attempt to cut the top for propagation, retaining the healthy upper part of the cactus for root growth.
Dehydration from Drought and Sun Exposure
Manifestation of Environmental Imbalance
Long-term water deficiency combined with strong direct sunlight causes the epidermis of the cactus to appear wrinkled and yellow, and the apical growth point to shrink. This situation often occurs during the transition periods of spring and autumn, when a sudden drop in air humidity accelerates water evaporation.
Gradual Watering Strategy
Use the immersion pot method to slowly add water, ensuring the water temperature matches the ambient temperature. After the first watering, place it in a scattered light environment and gradually increase the duration of sunlight after 3 days. It is recommended to mix 30% vermiculite into the potting soil to improve water retention.
Management Misconceptions During Dormancy
Physiological Cycle Characteristics
In winter, when temperatures drop below 10°C, cacti enter a dormant state, reducing their metabolic rate by more than 70%. Overwatering at this time can disrupt physiological balance and cause root frostbite and rot.
Overwintering Care Tips
Strictly control water from November to March of the following year, with a monthly micro-watering of no more than 20ml. Maintain a day-night temperature difference within 8°C and use a thermal film to cover at night. Gradually awaken the plant as spring warms up.
Prevention and Control of Diseases and Pests
Identification of Common Pests
Scale insects form a white waxy layer at the base of the spines, red spiders cause yellow-brown spots on the epidermis, and root mealybugs lead to the accumulation of fluffy substances on the soil surface, requiring targeted treatment.
Comprehensive Control Plan
Physical removal: Wipe the pests with a cotton swab soaked in 75% alcohol. Biological control: Introduce ladybugs to prey on aphids. Chemical control: Alternate the use of abamectin and imidacloprid, 7 days apart for 3 weeks. It is advisable to bury dinotefuran granules for prevention.
Through scientific diagnosis and precise intervention, more than 85% of yellowed cacti can recover. It is recommended to keep a care log, recording watering cycles and environmental parameter changes, and using a specialized substrate with more than 70% particle content, which can significantly improve the success rate of care.