Arbor Day is a nationally celebrated observance that encourages tree planting and tree care and highlights the importance of trees to our environment, our economy and our quality of life. Founded by J. Sterling Morton in Nebraska in 1872, National Arbor Day is celebrated each year on the last Friday in April.rbor Day is a nationally celebrated observance that encourages tree planting and tree care and highlights the importance of trees to our environment, our economy and our quality of life. Founded by J. Sterling Morton in Nebraska in 1872, National Arbor Day is celebrated each year on the last Friday in April.