All outdoor storage yards, permitted in the M-1 Limited Manufacturing District, shall be screened from all adjacent lots and street rights of way by a solid wall which shall be eight feet high and shall not extend beyond the front foundation line. As an alternative to the solid wall, the property owner or occupant may maintain a landscape buffer of evergreen and deciduous vegetation between the outdoor storage and the adjacent streets and street rights of way. It shall be the property owner's or occupant's responsibility to maintain the landscaping in good condition throughout the period of the use of the lot. Property owners or occupants who fail to maintain the landscaping shall be subject to the penalty in Section 764.99.