I think Bamboo is a grass rather than a tree - according to the Merriam-Webster dictionary "any of various chiefly tropical woody or arborescent grasses (as of the genera Bambusa, Arundinaria, and Dendrocalamus) including some with hollow stems used for building, furniture, or utensils and young shoots used for food". It's also the fastest growing plant on earth - you can even hear it grow. Next time you're at the Polynesian stand & listen.
I guess we'll have to wait till tomorrow to see who is right.
Bari