"Guttation

My houseplants are dripping water from the leaves. What causes this?

Your plants are taking in more water than they can use. This causes the leaves to excrete drops of water in the form of sap from the tips and undersides of the leaves. Sometimes this secretion may blacken or look translucent as the liquid dries. Another name for this phenomenon is guttation.

Reduce the amount of water you are giving the plants and increase the amount of light. This excess light forces the plants to utilize water. Increasing air circulation and lowering humidity will help in controlling guttation. Certain houseplants, such as dieffenbachia, are known for dripping water and this can be normal behavior."

-from the web site listed below

I've had large leaved tropicals like cannas, bananas, and elephant ears do this inside in the winter. I don't worry about it, just make sure the water won't damage any surfaces it drips on!

Here is a link that might be useful: guttation