"Ray" writes:
"Spanish moss" is the stringy bromeliad Tillandsia usnioides. It stays very
loose and springy when used to surround roots, so does not ever even think
about holding enough moisture to be "soppy."

Aha.

I need to go and see what I can get hold of, then. Right now, the
polyrrhiza is just lying on top of a sopping wet patch of the local
moss variant. The good news is that it doesn't contact the moss (yet),
but I will get rid of it anyway.

Geir