Fences, walls and hedges, as regulated in this and the following sections may occupy any yard and are required where specified in this title. The term “wall” as used in this connection shall not be deemed to apply to the wall of a building, or to the supporting portion of a retaining wall. The term “hedge” means cultivated plant growth along a line which is sufficiently dense to obstruct passage and visibility from one side to the other. (Prior gen. code § 8-60.53)