What is the difference between trees and shrubs?

There is no clear-cut distinction. However, a tree is commonly defined as a woody plant that reaches a height of at least 10 feet, has a single stem, and has a definite crown shape. A shrub usually is less than 10 feet tall and has several stems without a definite crown shape. Some specimens of plant species may take the form of a tree while others of the same species may take the form of a shrub-sumac and willows, for example.