“Arbor Day is a nationally-celebrated observance that encourages tree planting and care.

Founded by J. Sterling Morton in Nebraska in 1872, National Arbor Day is celebrated each year on the last Friday in April.

Yelm is having this town’s Arbor Day celebration from 11am until noon Friday, May 11 in Yelm Park.
Washington State’s Arbor Day is the second Wednesday in April.

The National Arbor Day Foundation has published a new hardiness zone map

The National Arbor Day Foundation has published a new hardiness zone map, based on climate data from the past 15 years, that clearly shows the warming trend across the country,” quoting the National Arbor Day Foundation website.