We grow a lot of trees at our nursery. Some of the bigger trees we grow are some maples, but the bulk of the larger trees are evergreens. Most are 4-6 foot, with only a certain few up to 7 and 8 foot. We have found this size transplants well. If you happen by at certain times of the year when Don is available, he will take you around the growing fields and you can pick your trees out while they are still in the ground.
Our tree spades dig out the trees when they are ready and then your tree will be balled and burlapped.