Root-bound if in a pot, or crowded in a tight clump in the ground, Ken. Those orange birds just don't want to bloom until they're crowded. I have one in my garden that I've been 're-habbing' for 3 years, and it's still not crowded enough to put up a bloom. As you say, the gorgeous clumps of blooming Birds you see in landscapes are very crowded, tight clumps. That's just the way they roll. Er, grow.
My agapanthus are the same way. If I rashly repot them, they take at least a year to bloom again, once they've filled in the spaces in the pot.
