Answer: Leaves turn yellow for a variety of reasons. Sometimes it's natural for leaves that are 2-3 years old to turn yellow and die. They're replaced by new leaves. Sometimes yellowing leaves are indication of disease or insect infestations. Or, yellowing leaves can be caused by overwatering, underwatering, too much, or too little
fertilizer. If you had the plant outdoors for the summer and recently brought it indoors, it could be suffering from the shock of its new environment.
Examine the plant carefully, looking for signs of insects and disease. Look on the undersides of the leaves and along the stem, and inspect the new growth. Could one side of the plant have been affected by something such as some errant herbicide or pesticide spray? Is that side facing a heater? If you can find any clues, feel free to submit another question via the web site and we'll try to help.
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