Hey Staver,
If it looks like bamboo/rivercane/reed, cut it and try making arrows out of it. Some of the stuff when you first cut it will seem too flimsy and weak to make a good arrow, but when it dries it will become much stiffer, denser, and tougher. I've been surprised more than once by how well certain materials will work for arrows.
I find some stuff here in Georgia that looks like phragmites reed, but I think it's a decorative reed of some sort. I've made arrows from it, and although it is somewhat lightweight, once it dries it makes excellent arrows. If it's straight and flies well, then it will work and that's all that matters!
By the way, I conducted some penetration tests on a freshly killed deer with one reed arrow, one rivercane arrow, and numerous foreshafts tipped with tiny birdpoints. I wrote an article about it and submitted it to Primitive Archer. It should be coming out in the next 2-3 months. I'm not going to give the results away, but the results were very surprising to say the least. It's titled "Putting Bird Points to the Test." Keep an eye out for it; it is the most interesting article I've written so far!