Arbor Day is a holiday dedicated to planting trees and helping them grow. People are encouraged to plant trees. Businesses and government programs may arrange communal plantings. Arbor Day was first proposed by Sterling Morton in Nebraska in 1872. It became a nationwide holiday in the U.S. in 1970 and is currently observed in many countries around the world.
National Arbor Day in the U.S. is observed on the 4th Friday in April. Many states in the U.S. celebrate Arbor Day on different days to correspond with the best planting time based on the climate of that state.