" wrote in
oups.com:

You probably have aphids or mealybugs, both are very common on
tropical hibiscus. What you are seeing is probably not sap, but
insect poop. On another note, sap production is a function of
staying alive, the only thing that would affect its production is
temperature.

Toad


Tanya might also be describing the result of extrafloral nectar that
some plants produce. It is generally used by the plant to feed ants
that would otherwise farm aphids on them. Extrafloral nectar is
generally produced in pit-like glands at the base of leaves, ends of
petioles, or other parts of the plant.

In addition to extrafloral nectar, some plants will produce fluid
under certain conditions. I refer to a process called 'guttation',
which usually occurs under very high humidity. This fluid is nearly
pure water.

Sean