After developing to their full size, each individual banana on your Grand Nain Banana Tree will stop expanding. At that stage, you'll notice that the small flowers that sit at the end of each banana are quite easy to rub off using just your hands. Those two signs are the best indicators that your banana bunch is ready for harvest. However, when in doubt, it's best to wait a bit longer to harvest as bananas that are picked too soon can not only lack flavor but also be difficult to eat.