The Windmill Palm is a medium growing palm tree. It is palm that has an unusual shape. The windmill palm?Aos trunk is thicker at the top than it is at the bottom. This palm has fan palm leaves but has longer stems that have no thorns. It grows up to an average of 20 feet high and is hardy to 12 degrees F. This description is based on our observations and research of this plant growing in our hot Arizona climate. We would love hearing from anyone who has any additional experience with this plant in Arizona.