I don't think what you have, is bamboo. Sounds like an aquatic grass of some type.

Whatever it is though, you can trim the parts you don't want without any problem. In my opinion, just don't trim more than 40 percent of the plant.

Good Luck

Kt

cassieg-
I agree with kentuck...bamboo does not grow in the conditions you describe. I'd be interested to see what you have, though. Can you post a picture here or in the gallery section of this forum?

Sounds like a horsetail rush (equisetum?)..... Not sure if you can trim it back or not.... Many people use horsetail rush as a bog plant, and it looks similar to bamboo. Maybe someone else here will have a little more info on that.

sounds like you might have arundo, not really a bamboo but more of a giant grass. does it have single leaves that look more like a culm sheath and dies back in winter?