How to Care for Phalaenopsis Orchids With Yellowing Leaves

Place the Phalaenopsis orchid in a location that provides bright indirect sunlight. Full sun can burn the orchid's leaves and cause them to turn yellow. Phalaenopsis orchids also grow well when placed under fluorescent lights. Place the orchid 6 to 12 inches beneath the fluorescent light. Leave the light on for 12 to 16 hours.

Maintain a room temperature of 60 to 65 degrees Fahrenheit at night and 75 to 80 degrees during the day. If the orchid becomes too cold, it will display yellow leaves.

Place the Phalaenopsis orchid in a saucer of moist pebbles. Raising the humidity around the orchid helps prevent yellow leaves. The orchid requires a humidity range of 60 to 80 percent to remain healthy.

Allow the potting medium around the Phalaenopsis orchid to dry out between waterings. The top 1 inch of soil should feel dry before watering the orchid. In the summer, water the orchid once every three days. During the winter, water the orchid once every two weeks. Make sure the pot has adequate drainage holes so the water flows freely out of the orchid's pot. A Phalaenopsis orchid that has excessively wet soil will begin to suffer root rot. The first sign of root rot is yellowing leaves.

Remove the Phalaenopsis orchid from its pot if it shows signs of root rot. Drench the orchid's root system in a fungicide that contains ophanate methyl. Re-pot the orchid in a new pot with new orchid potting medium. Avoid overwatering the orchid.