I've been wondering about this too. There are a number of red hibiscus bushes just across the street where I live. Each bush would flower sporadically, as in 1 or 2 flowers every now and then. Never a big crazy blooming frenzy.

Now these hibiscus bushes are neighboured by bougainvilleas and ixoras. Both species have been flowering like crazy since Apr, esp the bougainvilleas. Still, the hibiscus bushes aren't flowering (enough).