Bougainvillea are best left on ignore, :) If you fertilize they get huge and same if you over water, I just ignore them and occasionally pinch the tips off to make them more full.

Couldn't be easier than that... Thank you for your suggestion!

I always gave mine half strength fertilizer.

Let them become pot-bound if in pots, do not water often and a bloom booster fertilizer will also help. Ever noticed how in periods of long drought bougainvillea always flower well?

I've been watering weekly for some time... Have they been trained to require it now or do you think it's safe to break away?

Every other week should be fine. Also try Miracle Gro Bloom Booster fertilizer from HD. Full sun also helps

Hi
It's not that easy..i have tried all of the above suggestions. I planted many bougies. I tried ignoring them , hoping they would flower but they just sulked. I tried fertilizing, they dont do anything. I tried watering them, I got new leaves that dropped as soon as I stop regular watering. I took a few and stuck them in small pot near my potted roses. They got some water from me watering the roses and fertilizer as well. Right now they are nice, leafy and one of them is flowering. I think another one is about to flower. I"m not sure what it is that make them flower,coz ignoring them sure does not...

I have read that pruning helps as they bloom on new wood. A quote from a fertilizer website (which I have never tried, so I'm not promoting that)

"In Florida, landscape professionals commonly perform a hard cut at the first sign of summer, and keep on a regular trimming schedule all summer long to maintain size. Pinching is the method of removing the soft tips of young plant stems to encourage fuller growth. You can do this with a pair of secateurs, or by using your fingers to pinch off ý inch from the tip of new soft growth. Bougainvillea will send out several new stems just below the pinched tip.

The more regularly you pinch, the more your bougainvillea will branch and bloom. The best time to prune or pinch is after the flush of color or flowering cycle is completed. Flowering cycles are typically four to six weeks."

Here is a link that might be useful: fertilizer website