It shall be lawful for the owner or occupants of land bordering upon any public road to build sidewalks not to exceed six feet in width, to plant shade and ornamental trees along and in such road at a distance not exceeding one-tenth of the legal width of a road from its margin, and to erect and maintain a fence as long as it is actually necessary for the purpose of raising a hedge on the margin a distance of six feet from and within such marginal lines, except that when, in the opinion of the county board, the hedge fence, trees, or undergrowth on any county road interferes with the use of the right-of-way for road purposes or presents a hazard to the traveling public, the county board may, in its discretion, remove, or cause to be removed, at county expense, the hedge fence, trees, or undergrowth from the road right-of-way.