With all rational, Bougainvillea easily blossom in the tropics, that includes Singapore. But in our house, they don't. We have the violet, yellow and pinky white; only violet's getting the neighbors' attention - it blooms all year, without fertilizing.
Well, that wasn't the case, many years back.
The yellow and white were doing really well back then, together with violet. Then we had them uprooted, shifted to the adjacent ground; that was when the 2 boycotted till today.
We tried several flowering fertilizer from Malaysia; helpful neighbor also chipped-in to provide good fertilizers, but to no avail. Until a leftover pack of "Flowering Fertilizer for Bougainvillea" from an old neighbor came along - an old and tattered plastic package, i disposed of it as soon as i emptied the bag to a container.
Little do i expect it to work this time! It all happened within 3 weeks, with 2 occasions of light rain and minimum watering, when we finally saw the precious sight of yellow and pinky white flowers. Reunion with violet!
Pity i fail to document this fertilizer that worked. I'm sure it wasn't Bougain which is advertising so aggressively. The packaging looked more local with a few Chinese wording; and its granular, red feeding looked just like the Serbajadi 48. I'll try source it out locally and post it here. Meanwhile, try using the remainder sparingly...