Unlike water spots on African Violets, which permanently discolor the leaves, water spots on citrus trees are caused by mineral deposits in the water and leave a whitish discoloration which can be wiped away, much like water spots on glass dishes. Water spots do not harm the tree or hinder its development in any way, but they can reduce its beauty. Although some gardeners like to use mayonnaise to clean off water spots and polish the leaves, be aware that sunlight--even sunlight filtering in through a window--can burn the leaves of a tree treated with oil.
Water the soil instead of the tree. Indoor citrus trees should be watered when the soil is dry or mostly dry on top. Slowly pour water into the container until water starts to come out through the bottom holes.
During the drier winter, apply water to the leaves with a spray bottle that has a fine mist setting. You can also use a damp sponge to apply moisture to the leaves.
Remove water spots that do occur with a damp, soft cloth. Gently wipe the cloth against the face of the leaves. Neem oil, applied to the leaves, also removes water spots and helps to protect the plant against pests.