This is a horticultural technique of training a plant flat on a horizontal plane, for example against a wall or fence. It is often used for fruit trees or to grow a tree in a tight area. In terms of fruit trees it increases airflow and access to the fruit, making management a lot easier than growing as a regular shaped tree. Espalier is also used in courtyards or on walls, where space is a premium or to cover a wall.
You can train a number of plants to do this given the right equipment and patience. We also sell a range of espaliered plants already trained into shape and ready to go.