Whoever wilfully drives upon, picks, removes, destroys, cuts down, or in any manner injures any tree, shrub, plant or flower planted or growing within the right-of-way of any public highway, shall be guilty of a petty offense and fined not more than $100. However, the provisions of this section shall not preclude the highway authority having jurisdiction over the highway from trimming, transplanting, or removing such trees, shrubs, plants or flowers when necessary, in the discretion of such authority, to facilitate the use of such highways for public travel.