I would neglect it. Let it get very dry. That should encourage blooms. I havent had blooms on my bougainvillea for an entire year because I have been giving it lots of water so it gets to a good size and now that its at a good size I am now letting it dry out so it beings to bloom. Not sure if it will work, but I hear the more neglect, the more blooms for these plants.

Good luck!
-Alex

Agree- let it experience a dry season as it would in it's natural setting.

They grow like weeds here! It is very dry! Everybody has them on their stucco walls, and they grow in the bush form along highways. They do need a little water, but they love dry heat.

As TZ says, you need to try some TOUGH LOVE. Withhold your watering to the point of drought. You're probably overly fertilizing too. Containers that are too big may also be delaying bloom--everything is going into vegetative growth. Full sun, heat and some benign neglect is needed. PS., I learned this by keeping mine outside in full sun but well-watered all summer, result?--NO FLOWERS. When I would bring them inside in the Fall and forget about them, they would come into heavy bloom--without fail.