I have need for a large number of windbreak trees on an estate in southern Ohio. Cottonwoods are desirable because of the beautiful shape they develop, as well as the clapping sound of the leaves in the summer. No one, of course, likes the cotton flying in the pool and fountains. How reliable are cotton-less cottonwoods to truly be cotton-less? And if they are, where are the best places to buy, or varieties to buy, to ensure sterility of the tree.