I'm always confused between Arundo donax and Phragmites australis, because I think one of them is relatively common locally and I have used the slender canes as stakes. I'm thinking mine is actually Arundo or related, as Phragmites is supposed to be more compact and denser than what I've seen. The closeness of the leaves and fullness of your specimens makes me think that they are more likely Phragmites spp. I'm sure if I studied the inflorescence a bit more it would be clearer to me. Might your specimen fit either of these or related?
Arundo donax. Phragmites has much slenderer stems (~5 mm diameter) and leaves. @ thanrose - if the stems of yours are strong enough to use as stakes, you have Arundo too. Phragmites would be useless for stakes.
I'd never heard of Arundo donax; now I've just learned that it's the plant from which clarinet reeds (and other musical reeds) are made. Clarinet - Wikipedia
