From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-1886-940961
Question: I recently bought a bouganvilla plant in a hanging basket
after I came across a gorgeous picture of one growing over the
balcony, full of gorgeous blooms. How can I get mine to grow like
that? Can it grow year-round here in North Carolina? It doesn't snow
often in our area, but we do have hard freezes.
Answer: In warm winter areas bougainvillea can reach outstanding
proportions. However, in your gardening region you'll need to consider
them as annuals, or plan to nurture them all winter by providing
protection from frost. Sometimes bougainvillea can be grown as
houseplants, or at least kept alive indoors, and taken back outside
when weather warms.
For now, provide your plant with full sunshine, keep the soil moist
but not soggy wet, and prune back the shoots when flowers fade.
Bougainvillea flowers on new stems and they are quite vigorous
growers. The more you prune, the more flowers your plant will produce.
If you decide to overwinter your plant indoors, keep it well watered
during the spring and summer months then taper off on watering in
early fall. Before nighttime temperatures drop below 45F take your
plant indoors and place it in a sunny window, in an unheated room.
Keep the soil almost dry during the winter, then increase the
temperature and watering once spring arrives. When all danger of frost
has passed, take your bougainvillea back outdoors.