Wow! I didn’t know that...
Bamboos – and, in fact, all grass plants – are pollinated by wind, not insects.
Unlike trees and woody plants, a bamboo shoot cannot expand sideways, so when it emerges at soil level, it is already at its maximum thickness.
If you find it difficult to get your head around the clump or running-bamboo rule, you’ll be sorry to learn that forms of phyllostachys bamboo tend to be clump-forming in the cooler conditions of Britain, but can develop a ‘running’ habit if planted in warmer areas, like southern Europe!