Hi there. I'm curious as to your zone. In colder zones, plants need to be grafted onto hardier stocks.

Japanese willows -- any willows do not produce flowers - instead they give out catkins in spring. Often Hakuro Nishiki (Japanese Willow) in tree form are grafted. The top isn't the same as the bottom plant It does produce white leaves which when still young appears as pink. It may look like flowers but they are leaves in fact.

Was this a grafted tree? Was this originally sold as a standard tree? If the top dies, then the bottom starts to produce it's own leaves and branches. I don't know what species the bottom is.