Rubber plants (Ficus Elastica) are native to Southeast Asia, but grown as houseplants around the world in any climate. The evergreen plant has leathery, dark green leaves that appear to have a glossy finish. Rubber plants require minimal care to grow, but plants can experience some problems that will cause the leaves to turn yellow.
Overwatering the rubber plant can result in yellow leaves. Plants need moist soil, but if the soil is wet or soggy all the time, the leaves will start turning yellow and drop from the plant. Plants need water when the top 2 inches of the soil is dry to the touch. If the container has a drainage tray underneath, the tray should have gravel inside of it to keep the container out of the water.
Drafty and Dry Air
Drainage trays filled with gravel placed under the plant container will provide humidity around the plant. The rubber plant leaves will turn yellow and drop from the plant if the air is dry. Drafts from doors and cooling systems will cause the leaves to turn yellow. Plants are adaptable to many indoor conditions, but drafts will shock the plant and cause the leaves to turn yellow and drop.
The fungus powdery mildew will cause the leaves to turn yellow and look distorted. Powdery mildew appears as a white, dusty powder on plant leaves. Discard leaves that drop from an infested rubber plant to stop the spread of the fungus. Use a product with neem oil or potassium bicarbonate to combat the fungus on the plant leaves.
When rubber plant roots absorb water faster than what the plant uses it will suffer from oedema. The water pressure builds up in the leaves causing blisters on the stems and leaves. If the problem continues, the plant leaves will turn yellow and drop from the rubber plant. Oedema usually happens in the winter when wet, warm soil mixes with wet, cold air. Avoid this problem by reducing watering and humidity levels during cooler months.
Rubber plants that become overly pot bound will begin to have yellow leaves at the bottom of the plant that drop from the plant. Adding nitrogen fertilizer to the soil to encourage green foliage or repotting the plant in a container 1 to 2 inches in diameter larger than the current container will stop the plant leaves from yellowing and dropping.