Overwintering Tropical Plants

You can overwinter many tropical plants by just bringing them inside for the winter.  I have a six-year old hibiscus that resides, and blooms, in my living room until later April.  The only problems I have had is that the plants, unless given supplemental light, may look ragged and tired by the end of winter and we get fungus gnats, tiny and annoying, but not harmful, bugs.  I recently began using a BT (Bacillus thuringiensis,  http://en.wikipedia.org/wiki/Bacillus_thuringiensis) product from Gardens Alive  (KnockOut granules
http://www.gardensalive.com/product.asp?pn=3440  ) that is organic and harmless to all but the gnats and it seems to be effective.
Overwintering an aquatic (pond) tropical plant is a different matter. I have been overwintering an umbrella palm (photo above) for several years.  Umbrella palms are easy to root, just cut off the long stem and place the "umbrella" in water, but these take a few years to get to a decent size, hence I bring it in from the pond. I have also overwintered floating water hyacinth with success.  These plants are overwintered in an out-of-the- way place, my attic, as they are not very attractive and can get a little smelly (change the water if this happens).  They need supplemental light, under hanging florescent tube lights.They need a sturdy container that does not leak and holds a sufficient amount of water to keep the plant alive.  Here I am using a crisper drawer from a long-defunct fridge (Reuse, Reduce, Recycle!).  It is sturdy and clear and I can check the water easily for bugs.  I do not bring in pond water- this guarantees bugs, and perhaps hatching mosquitoes, in your house! I use tap water, with the proper amount of a de-chlorinator sold for ponds, or cholrine-filtered water.
So, plan to bring those tropical plants inside in the future (BTW, I brought this umbrella palm indoors on 11/26- the pond retains heat and it was still unfazed by the cold!)
Happy gardening!