C.R.S. § 24-11-104: Arbor Day - tree planting.

The third Friday in April of each year shall be set apart and known as "Arbor Day", to be observed by the people of this state in the planting of forest trees for the benefit and adornment of public and private grounds, places, and ways and in such other efforts and undertakings as shall be in harmony with the general character of the day so established.