Yellowing of leaves can be caused by normal aging, lack of sunlight, overwatering, nutrient deficiency, color drafts and viral infection, according to About.com. When plants age, it is normal for their leaves to turn yellow and eventually drop off.Continue Reading
Overwatering is one of the most common causes of yellowing of leaves. Most plants don't grow well in mud, except for semiaquatic plants. Moreover, if the plant does not receive sufficient sunlight, the leaves away from the sunlight may start to yellow.
A common sign of nutrient deficiency is when the yellowing follows an unusual pattern or when the top leaves are yellowing. A viral infection might be the cause if the plant has blotchy yellow patches. The spreading of these patches can be accompanied by deformed leaves and stems.Learn more about Trees & Bushes