R.I. Gen. Laws § 45-2-43: Right of way tree planting.

Cities and towns may appropriate resources to be used under the direction of the tree warden in planting shade trees upon land adjoining public right of ways, at a distance not exceeding twenty (20) feet from the public ways, that will function as public trees by improving, protecting, shading or beautifying the right of way; provided, that the written consent of the owner of the adjoining land is first obtained.