That's interesting re Frog Bit. It dies back here and never comes back, zone
7a. Maybe for all the zone 8-ers on the coast. Was being sold here last year
for $3 a little plant!!

It dies back here also, but comes back strong every year. It sinks to the
bottom of the pond and then floats up in spring....Maybe your pond bottom is
too clean ....Mine does not come back in the koi pond, only the lily pond....I
think the koi eat it.....I am in zone 7 Jerri

http://www.fringeweb.com/Ponds/JerrisPond