When is the best time to split birds of paradise?

Hi
When is the best time to split a bird of paradise? I heard it is Spring, but it is flowering and I want to be sure I split the plant at the best time. It has been in the ground for many years and is quite substantial. Originally it was split from my grand aunts bird of paradise in the 1960s. .. so it is extra special and family want to share.
Look forward to your reply
Many thanks