No person, firm or corporation shall interfere with the director or persons acting under his authority while engaged in planting, mulching, pruning, trimming, spraying, treating or removing any tree, shrub or plant in any street, park, parkway or public place within the city, or in the removing of any stone, cement or other substance from about the trunk of any tree, shrub or plant in any such street, park, parkway or public place. (Ord. 4122 § 1, 2003; prior code § 12.36.070)