Why doesn't a potted pomegranate bloom?

The early summer breeze stirs my thoughts. Casually, a few pomegranate plants in the yard sway a few small orange-red flower buds here and there. The weather is unpredictable, now sunny with bright sunshine, now drizzling rain. Within a few days, pomegranate flowers all over the trees, like clusters of leaping flames, come into my sight.