Plant Trees Now

American Forests, a not-for-profit association based in Washington, has maintained the National Register of Big Trees for over 50 years.

American Forests uses a three-part formula—based on girth, height and crown spread to rate a tree by size and determine which is the champion — the biggest.

The current National Register lists over 800 tree species with a recognized National Champion.

But that is only a by-product of its work. American Forests works to protect, restore and enhance the natural capital of trees and forests.

"Healthy forests filter water, remove air pollution, sequester carbon, and provide homes for wildlife," it says. "Help plant trees to restore areas damaged by wildfire, where critical wildlife habitat has been lost, and to clean our air and water."

You can also learn how you can plant a tree in your backyard with the step-by-step rules of tree-planting listed on its site.