In most cases if a house plant is already receiving adequate light the use of window film will not harm it. New growth or flowering may be retarded, and, for a few days, a plant may go into a state of shock while it adjusts to the light change. If a particular plant normally wilts by the end of a sunny day, it will actually thrive better with film installed. Although there are some obvious guidelines in determining what, if any, effect window film will have on a plant (for instance, dark green plants need less light than lighter colored ones), there is one sample test which can be done prior to film installation; that is, merely move the plant to an area with less sunlight for a few days. In addition, most nurseries or local agriculture agencies can advise you whether a particular plant needs closer to maximal or minimal light.