Except to abate a nuisance as defined in this chapter, it is a violation of this chapter to damage, destroy or mutilate any tree, shrub or plant in a public parking strip or any other public place, or to attach or place any rope or wire (other than one used to support a young or broken tree), sign, poster, handbill or other thing to or on any tree growing in a public place, or to cause or to permit any wire charged with electricity to come in contact with any such tree, or to allow any gaseous, liquid or solid substance which is harmful to such trees to come in contact with their roots or leaves; provided, however, that nothing contained in this section shall preclude either the owner or occupant of real property from trimming or removing trees, shrubs and plants in the parking strip of such real property. (1957 code § 8.15.080.)