Topiary

Topiary is the horticultural practice of training perennial plants by clipping the foliage and twigs of trees, shrubs and subshrubs to develop and maintain clearly defined shapes, whether geometric or fanciful. The term also refers to plants which have been shaped in this way. As an art form it is a type of living sculpture. The word derives from the Latin word for an ornamental landscape gardener, topiarius, a creator of topia or "places", a Greek word that Romans also applied to fictive indoor landscapes executed in fresco.

The plants used in topiary are evergreen, mostly woody, have small leaves or needles, produce dense foliage, and have compact and/or columnar (e.g., fastigiate) growth habits. Common species chosen for topiary include cultivars of European box (Buxus sempervirens), arborvitae (Thuja species), bay laurel (Laurus nobilis), holly (Ilex species), myrtle (Eugenia or Myrtus species), yew (Taxus species), and privet (Ligustrum species). Shaped wire cages are sometimes employed in modern topiary to guide untutored shears, but traditional topiary depends on patience and a steady hand; small-leaved ivy can be used to cover a cage and give the look of topiary in a few months. The hedge is a simple form of topiary used to create boundaries, walls or screens.

...
Wikipedia