Let's define the terms:
(1) Edge: An edging or border is typically a low line of plants used to define the boundary of a path, lawn, or flower bed. It's usually much lower than a screen.
(2) Hedge: A hedge is a line of closely planted shrubs or trees, grown and usually trimmed to form a continuous barrier, screen, or boundary. Hedges can vary in height from low formal hedges to tall screening hedges. The key aspects are close planting at regular intervals and forming a continuous screen or barrier. This perfectly matches the description.
(3) Arches: Structures, often made of metal or wood and covered with climbing plants, that form an archway over a path or entrance. Not a continuous screen of shrubs/trees planted in a row.
(4) Pergola: An outdoor garden feature forming a shaded walkway, passageway, or sitting area of vertical posts or pillars that usually support cross-beams and a sturdy open lattice, often upon which woody vines are trained. Not a continuous screen of shrubs/trees.
Therefore, shrubs or trees planted at regular intervals to form a continuous screen is called a hedge.
Hedge