What Causes the Yellowing of Orchid Leaves
As a traditional famous flower in China, yellowing of leaves during the orchid cultivation process is a common issue. This article analyzes the causes of yellowing leaves in orchids, from nutrient management to environmental control systems, and provides operational solutions to help you cultivate high-quality orchids with lush green leaves.
I. Nutrient Imbalance Leading to Yellowing Leaves
1.1 Mechanism of Nutrient Deficiency
Orchid roots are fleshy aerial roots. When deficient in nitrogen, phosphorus, and potassium, the older leaves first show uniform yellowing. Long-term failure to change the growing medium or the use of a single fertilizer can lead to a deficiency of trace elements,表现为 new leaves with yellowing between the veins.
1.2 Scientific Fertilization Plan
Apply orchid-specific slow-release fertilizer monthly in spring and autumn, combined with foliar application of chelated iron fertilizer. Stop fertilizing during the high-temperature period of midsummer, and switch to phosphorus-potassium fertilizers in winter to enhance cold resistance. After fertilizing, rinse the leaf heart with clean water to avoid fertilizer damage.
II. Improper Light Management
2.1 Analysis of Light Intensity Impact
Black orchids and Cymbidium need a 30% shading rate, while spring orchids and Eulophia need a 50% shade net. Direct sunlight for more than 3 hours can damage the chloroplast structure, causing sunburn-like yellowing leaves, and severe cases can lead to entire leaves drying up.
2.2 Techniques for Light Adjustment
Use an adjustable shading system, providing shade from 10:00 to 15:00 in summer. An east-facing balcony is most suitable, and if south-facing, a bamboo screen needs to be added. In winter, full sunlight can be accepted to promote bud differentiation.
III. Key Points of Water Management
3.1 Identification of Root Rot due to Water Accumulation
The characteristic of water yellowing is that the leaves turn yellow from bottom to top, and the roots turn brown and rot. The three main causes are compacted growing medium, pots without bottom holes, and excessive watering, which often occur during the plum rain season.
3.2 Scientific Watering Method
Use the immersion pot method to supply water, and water again when the top 2cm of the growing medium is dry. Use a mixture of snake wood chips and volcanic rock (3:7) as the growing medium, and choose a purple sand pot with a high foot to enhance breathability.
By precisely adjusting the three elements of water, fertilizer, and light, combined with regular replacement of the growing medium, checking the roots, and other maintenance measures, yellowing of orchid leaves can be effectively prevented. It is recommended to apply EM bacteria solution every quarter to improve the rhizosphere environment, use a light meter to monitor light intensity, and achieve scientific and precise management.