I had several bouganvillas when I lived in Phoenix and all I can tell you is that they like it DRY. The less water you give them....the more they bloom. I really miss those beautiful plants and am anxious to see how yours do up here in the northwoods!!!

I wonder if the fertilizer wasn't enough to overcome "tired, old soil". You might try repotting them, although it's a little late in the season. If that doesn't do it, it's gotta be other cultural practices...

Hi there-
I had wondered if they might behave like poinsettias with needing special light conditions to prompt bloom- With what this article says- I believe it may just need brighter light-

Hope this helps-

Julie

Here is a link that might be useful: This may help-

I know it's been a while since you posted re: bouganvilla. I have one in a basket that is about 6 or 7 years old, and it blooms 2 or 3 times a year. In the summer, I hang it outside on my patio and before the first frost, I bring it in and put it in a East facing window. I only water it about every two weeks. If the leaves start to dry and fall off, it is telling me that it needs water. Be sure to keep it away from any heat from the furnace since the draft will dry it out quickly.