There is a Bamboo section under Trees and Shrubs. Of course Oron is right that as glorified herbaceous plants they are really "perennials". As I said when I put that section in Trees and Shrubs, "Though bamboos are I supposed really just jumped-up grasses, most people do think of them more as shrubs - or, for the giants, even trees."
So I rather agree with John. If no-one disagrees, I shall move this whole discussion to the main Bamboo section back in Trees and Shrubs.