Who is right about height?

I’m thinking of buying two Phyllostachys nigra from Thompson & Morgan. They state that they grow 3m (10ft) high, your book Plant Solutions tells me they grow to 8m (27ft), The RHS Encyclopedia says 6m to 8m (20-27ft). Who is right? Can you also suggest any other bamboo?

Need you ask? The height given by me and the RHS refers to the plants’ ultimate growing height, given good growing conditions in open ground. They will not grow so tall if you grow them in a container. They will also be less tall grown in poor soil.
If you want a stately plant, choose P. nigra, but if you don’t want it to exceed 3m (10ft), grow it in a big pot or a tub.