the trees needs alot of iron, when the nail starts rust its putting the iron back into the ground and into the base of the tree. take where your limbs come out of the tree on the farthest point and place the nails into the ground,this is where the roots of the tree are ending. put a dozen or so into the base of the tree, and place about 12inches apart into the ground. you will be amazed at what it does for fruit trees. like i said before it gave me 50% more apples on the trees.