There are several types of ficus plants --including ficus elastica, commonly known as the rubber tree plant. The type most recognised as simply a "ficus plant" or "ficus tree" are actually the ficus benjamina or "weeping fig." Ficus benjamina plants are notoriously finicky, and are known to drop leaves in protest of various unfavourable or unsatisfactory conditions.
Ficus plants are tropical plants whose natural habitat includes quick-draining soil. These plants do not like sitting in soggy, waterlogged soil. An overwatered ficus drops newly developed green leaves and leaves from the tips of the branches. To avoid overwatering, use a flower pot that has a drainage hole on the bottom and do not use a saucer to catch excess water. If the plant is over carpet or other flooring that could be damaged by draining water, place the pot on a stand and place a saucer or other vessel on the floor underneath. Water your ficus only when the top inch or two of soil is dry to the touch. The ficus will likely continue to drop leaves for a couple of weeks, but new growth will begin to appear once the plant is stable again.
Only the top inch or two of a ficus plant's soil should be dry before the next watering. If several inches of soil are dried out, the ficus plant's leaves will turn yellow and drop off. An underwatering problem is best fixed with more water given at each watering, not more frequent waterings. According to the University of Nebraska-Lincoln, if the ficus dries out too frequently despite adequate waterings, a too-small pot may be the culprit, because there is not enough soil to retain excess water. This is easily fixed by repotting into a larger pot with more soil.
Ficus plants are tropical plants that love warm climates. Ficus plants in colder climates protest cold drafts by dropping healthy green leaves. If your ficus is near a draughty window or door, apply gaskets or draft guards to keep the ficus in as warm a temperature as possible.
Ficus plants are sun lovers that prefer intense lighting for at least 8 hours per day. A ficus in a shady section of the yard, or in a dimly lit room, will begin to drop leaves very quickly, until it is moved to a brighter location. Outdoors, place a ficus plant on the western or southern side of the yard for the best lighting; indoors, place your ficus by a window with southern exposure, or use plant lights.
Ficus plants are very particular, and like to maintain the status quo. If a ficus is moved from one location to another, it will drop its leaves to show its disapproval. You can reduce the number of leaves dropped by moving the plant gradually, to acclimate it to its surrounds slowly. If you want to move the ficus from one side of the house to the other, for example, move it a few yards at a time, leaving it in each spot for a few days before moving it a few yards more. If the move is sudden, the ficus may drop all of its leaves, but will grow them again if you maintain proper watering, light and temperature conditions.