Okla. Stat. tit. 2, § 16-68
The last full week in March of each year shall be known throughout Oklahoma as Arbor Week.
Laws 1971, SB 143, c. 349, § 312, emerg. eff. June 24, 1971; Amended by Laws 1982, HB 1856, c. 40, § 1, emerg. eff. March 26, 1982; Renumbered from 2 O.S. § 1301-312 by Laws 2001, SB 522, c. 113, § 56, emerg. eff. April 18, 2001.