Although I am very fond of the leaves, this tree is mostly grown for its showy, puffy flowers. The Calliandra should be kept at a temperature of at least 18C ( 65F) . Bring it outside for the summer as this this a high light tree ( 6 hours ) and in the winter you'd to well to add some extra lighting.
When the top of the soil dries out, water as this tree likes to be on the moist side
But its worth it!