Reasons Why Phalaenopsis Leaves Turn Red and How to Handle It

Phalaenopsis orchids (Phalaenopsis spp.) are beloved by flower enthusiasts for their elegant blooms, yet during care, the phenomenon of leaves turning red occurs from time to time, caused mainly by multiple factors including light, water, temperature, nutrients and disease.

Light

When Phalaenopsis orchids are exposed to excessively strong light, the leaves show obvious physiological reactions. New leaves tend to develop purplish-red patches or localized red spots, accompanied by slight shriveling of the leaf surface. This is because overly strong ultraviolet rays destroy the chlorophyll structure within the leaves, causing anthocyanins to become visible, which in turn discolors the leaves.
 
Solutions:
 
1. Light adjustment: immediately move the plant to a spot with indirect light and avoid direct sunlight. You can choose an indoor spot 1 - 2 m from a window, which ensures sufficient light while avoiding direct-light damage.

2. Summer protection: during the hot, strong-light periods of summer, use a shade net with a 60% shading rate to provide shade, creating a suitable light environment for the plant.60%shade net for shade treatment, creating a suitable light environment for the plant.

3. Transitional adaptation: when the light environment changes, adjustments must be made gradually, giving the plant a 3 - 5 day adaptation period to prevent growth disorders caused by sudden environmental changes.

Watering

Overwatering: excessive watering keeps the growing medium in a highly moist state for a long time, hindering root respiration and thereby causing root rot and reddening of the leaves. At this point, the sphagnum moss and other medium feels wet and slimy to the touch, and on parting it the roots can be seen to be blackened and rotting.

Solutions:
 
1. Restrict water and change the medium: stop watering immediately, and wait until the medium is completely dry before the next watering. At the same time, replace the medium with one that has good air permeability; a mixed medium of sphagnum moss and bark is recommended to improve drainage and aeration.

2. Root treatment: if the root rot is severe, remove the plant from its pot, trim away the rotten roots, soak it in a carbendazim solution for disinfection, and then repot it.

Improper watering method: watering directly into the crown of the plant easily causes water to collect there; in a hot, humid environment this provides a breeding ground for bacteria and fungi, triggering crown rot, which manifests as reddening and rotting of the crown.

Solutions:
 
1. Water along the pot edge: when watering, pour slowly along the edge of the pot to prevent water from entering the crown.

2. Prompt treatment: if water is accidentally poured into the crown, immediately blot up the accumulated water with highly absorbent paper towels, or use a fan on low speed to dry it.

Temperature

Low-temperature cold damage: the suitable growing temperature for Phalaenopsis orchids is 16 - 30 °C; when the ambient temperature falls below 10 °C, the plant's metabolic functions become disordered, the leaves take on a reddish hue, and in severe cases the leaves also become soft and suffer frost damage.

Solutions:
 
1. Temperature control: in winter, place the plant in a warm environment and keep the room temperature stable within the suitable range. During cold waves, you can wrap the pot with insulating film or a plastic bag (with ventilation holes left) to keep it warm.

2. Keep away from cold sources: avoid placing the plant in locations with large temperature fluctuations, such as beside windows or air-conditioner vents.

Nutrition

Potassium deficiency: potassium plays a key role in plant photosynthesis and stress resistance. When Phalaenopsis orchids lack potassium, the edges of old leaves first turn red, gradually spreading toward the middle of the leaf.

Solutions:
 
1. Foliar spraying: dilute monopotassium phosphate 2000 times (that is, 1 g of fertilizer mixed with 2 L of water), and apply a foliar spray once a week to promote rapid absorption by the plant.

2. Long-acting fertilisation: use a slow-release fertilizer in combination, which releases nutrients slowly and provides continuous nutritional support for the plant.