I'm in zone 8 and they wouldn't winter in the ground here. I cut them off and mulched them well and they still died. I think that you have to be at least a zone 9 for them to live over the winter in the ground.

Bring them into a garage or similiar area, cut back on water and let them go dormant. They will die back some, but in the spring cut back the branches, water well and move outside, gradually moving them into full sun. While in the garage water just enough to keep th soil barely damp. I watered mine maybe a little every 2 0r 3 weeks.

Jackie, CONGRATULATIONS. Take good care of yourself and little Jackie or Jack. Bougainvillea is pretty but it is full of sharp thorns. It is hard to handle it without getting a painful sticking - OUCH. I had trouble getting them to rebloom as well. I don't want anymore of them. Keep us updated about the baby! -

The secret to reblooming bougainvilleas is to let them dry out almost to the point of wilting. Let the leaves turn that greyish green. Water them well and then fertilize them 1 tsp/1gal H20 of 10-30-20. The dry spell is what triggers bougainvilleas to bloom.You may have to fertilize them like this for a month or so to get them to start back blooming.