You can prune back anything you want. It just might not look great because bamboo are not like trees and bushes. What you prune back is gone and will not be replaced by other branches or more leaves. Each culm reaches its maximum size in the growing season during which it first emerges. It will never get taller, wider, or bushier. So just keep that in mind as you do your chopping...

Yeah, they don't look quite as good when you top them, but it's not really bad at all. And the nice thing is that once you cut them, they won't ever regrow. Imagine that, once pruned... they stay pruned! Of course, the next year's culms will reach for the sky.

Pruned forever sounds good! Thanks all.