An Arava that was stolen or dried out it is pasul if it came form an asheira tree or ir hanidachas it is pusal. If the top was cut off or the leaves were cut off or it came from a plant where the leaves are more rounded it is pasul. If the leaves were wiltetd or some of the leaves fell off or grew ina rain watered field it is kosher.

Succa 3:4

Rebbe Yishmael says you need three hadasim two aravos one lulav and one esrog. The three hadasim, two of them can be cut on the top. Rebbe Tarfon says even all three can be cut at the top. Rebbe Akiva says just like you have one lulav and one esrog the same you have one hudas and one arava.