Commercially produced plants are grown to many specifications. Smaller plants are usually container grown, however large trees are generally grown in the field, dug, and then balled and burlapped (B&B). The standard way of comparing trees over 8 feet tall is called Caliper. For nursery-grown trees, this a measurement of trunk diameter, in inches, taken 6 inches from the rootball.
Trunk Caliper can be used to predict the overall size of tree, and the size of its root ball. Professional landscapers use this information to order trees when they can’t go out to the farm to see them in person.
The speed that trees reach salable size in the field varies between species. Also, different species require specific rootball volumes to transplant well. A tree with a 2″ caliper can be expected to have a rootball weighing around 400 lbs! If you are investing in a tree for your yard, speak to a professional landscaper who will be able to recommend what size you can handle and still meet your needs