What Causes the Yellowing of Cattleya Leaves
As a noble lady in the orchid family, the yellowing of Cattleya leaves often leaves caregivers at a loss. This tropical orchid plant is extremely sensitive to its growing environment, and changes in leaf color often indicate a chain reaction from the roots to the crown. This article will systematically analyze five typical causes of yellowing leaves to help you accurately diagnose plant diseases.
Yellowing Symptoms Caused by Water Imbalance
Overwatering (Water-induced Yellowing)
When the saucer accumulates water for more than 48 hours, the oxygen content in the substrate drops by 60%. At this point, the fibrous roots become transparent and rot, and the tips of the young leaves show waxy dark yellowing. It is recommended to use the bamboo skewer test: insert the skewer into the substrate for 2 hours, and if it brings out mud, stop watering.
Long-term Drought (Drought-induced Yellowing)
The lower old leaves turn yellow from the edge towards the midrib, which is a signal that the plant is activating its self-protection mechanism. Soaking the pot for watering is beneficial for the roots to absorb water completely, and pay attention to controlling the water temperature between 25-28°C to avoid large temperature differences that damage the aerial roots.
Yellowing Phenomenon Caused by Nutritional Imbalance
Over-fertilization (Fertilizer-induced Yellowing)
Excess nitrogen will make the leaves thick and curly, with brownish yellow spots between the veins. Emergency treatment can involve spreading 3cm thick vermiculite to absorb excess nutrients, or transplanting to a new ratio of pine bark substrate.
Deficiency Symptoms
Lack of magnesium causes old leaves to show net-like yellowing; insufficient iron leads to new leaves turning white. It is recommended to supplement with orchid-specific nutrient solution containing trace elements every month, diluting the concentration to 1200-1500 times.
Yellowing Issues Caused by Environmental Stress
Acid-alkaline Imbalance (Alkaline Yellowing)
In northern regions, the pH value of tap water is generally >7.5, which can lead to salinization of the substrate over time. Actual test data shows that after watering with fermented rice washing water (pH 5.8) for three consecutive times, the substrate pH can drop from 7.2 to 6.5.
Improper Lighting
Direct strong light can cause yellow burn spots on the leaf surface, while insufficient lighting leads to overall yellowing of the plant. It is recommended to receive full sunlight in spring and winter, set up 40% shade netting in summer, and maintain a light intensity of 15000-20000Lux.
Mastering the ecological code behind the yellowing of Cattleya leaves can help this tropical beauty regain its vitality. It is recommended to perform leaf surface inspections monthly and monitor the root environment with a substrate EC value tester. When you find that the new flower spikes start to color, it indicates that the adjustments in care have begun to show results.