The owner of any property within the City on which shade trees are planted or growing shall trim and maintain the branches of the trees so that such branches shall have a clear height of at least eight feet above the surface of the sidewalk and eighteen feet above the surface of the roadway. If any owner fails to comply with this section, such trimming may be done by the Service Director and the cost thereof charged against the owner and collected in the manner provided by law. The payment of such expense shall not relieve the owner from the penalties hereinafter provided. (1964 Code Sec. 52.17)