The leaves are falling off my Schefflera, Umbrella Tree as well. The leaves aren't turning yellow or brown. They look completely green and healthy until they are laying on the floor looking sad. My plant isn't very large (2 1/2' tall) and this loss of leaves is happening all over the plant.
I water from the top when the top 1 or 2 inches is dry. Although my pot doesn't have a saucer, it has a fews holes drilled into the bottom lip of the plastic pot. There are some rocks in the bottom for drainage as I recall, but the plant hasn't been repotted for 4 years. It was repotted in a pot much larger than it's last pot though (probably too large).
I have been using a house plant fertilizer with each watering recently. This problem occured before I started using the fertilizer and continues after.
It is indirect but fairly bright light.
Also I mist the leaves daily because my place is fairly dry.
I really hope you can help me. I really love this plant and it is losing leaves fast. Thanks!