Q.What Causes A Bougainvillea Plant To Quit Blooming?
I live in central California and in the spring my bougainvillea blooms profusely! Then it tends to quit blooming but continues to grow and look healthy. Is it a watering issue? Too much or not enough? Should I fertilize?

The lack of water can force blooming as the plant tries to develop seeds in case of death so, try not to over-water as that can inhibit flower production. Also, make sure that you are not using a high nitrogen fertilizer as that produces lots of nice green foliage and few/no flowers. A potted Bougainvillea can be thoroughly watered but then wait for top soil to dry a little bit before watering again. Local environmental conditions may require tweaking that.

Insufficient sunlight, transplanting, too much high nitrogen fertilizer or too much water will do that.