To thrive, schefflera needs a medium amount of indirect bright light -- 200 or more foot-candles -- for at least 12 hours each day. Foliage grow lights can help provide adequate light during winter and in low-light situations. Schefflera will quickly drop leaves in response to reduced light intensity or reduced light duration, which occurs during winter. If light is adequate but a schefflera previously grew under truly optimal circumstances, leaf drop may still occur -- a possibility you can prevent by allowing the plant to gradually acclimate or adjust to lower light levels. With gradual light reduction, old leaves may drop but new ones will emerge that are better adapted to the setting.
Scheffleras can be overwatered either by watering them too frequently or by using too much water -- or both. Soggy soil can cause bacterial root rot, which in turn causes leaves to drop. Water the schefflera enough to completely soak the soil -- pouring out all excess water once the soil has drained -- but don't water again until the soil dries out somewhat. However, allowing the soil to get too dry, to the point that schefflera wilts, may cause lower leaves to drop if it happens too often. During the winter rest period, water plants just enough to keep soil from drying out completely.
A schefflera will lose leaves in winter due to cold air drafts and also hot, dry air. Locate your schefflera in a place well away from cold windows and doors opening out into cold weather and also far from wood stoves, fireplaces, ovens and heater vents. After adjusting a schefflera's environment -- and assuming its light and water needs are well met -- the plant may produce new leaves.
Even when its growing conditions are reasonably good, as a schefflera grows taller it may lose its lower leaves. Plants will also lose their lower leaves in response to lower light intensity; they may also get tall and lanky. You can revitalize a schefflera by air layering the top part of the plant -- to propagate a new plant from it -- while it is still attached to the parent plant. Once the top is removed for planting, the base of the parent plant will usually generate new growth from the base.