What is a tree vs. shrub?
As defined in the Checklist, trees are woody plants with one erect perennial stem or trunk at least 9 inches in circumference (3 inches in diameter) at 4 feet above the ground (breast height), a definitely formed crown of foliage, and a height of at least 13 feet. In contrast, shrubs are small woody plants, usually with several perennial stems branching at the base.