Each town or city may appropriate annually sums of money to be expended by the tree warden of a town or city in the planting, trimming, spraying, care, and preservation of shrubs or ornamental or shade trees within the limits of any public highway or grounds under his or her control and, at the discretion of the tree warden with the written consent of the owner, upon land adjoining any public highway or grounds, if not more than twenty (20) feet from the highway or grounds, for the purpose of shading or ornamenting highway or grounds.