Step 1: An East-West hedge keeps one side (north) shaded for most of the day, since the shadow barely moves.
Step 2: A North-South hedge throws its shadow east in the morning and west in the evening, so the shadow keeps shifting and no side stays dark all day.
Step 3: Diagonal layouts (NE, SE) only give partial, uneven benefit of this shadow movement.
Step 4: Hence the correct orientation is North-South.