What is the term for training fruit trees to grow flat against a wall or trellis? The technique is called espalier.
In espalier, gardeners prune and tie a woody plant’s branches to wires, a frame, wall, fence, or trellis so the plant grows in a largely two-dimensional pattern. The method saves space and can make fruit easier to inspect, prune, and harvest. A wall may also reflect sunlight and retain heat, helping fruit mature in cooler climates.
The practice is ancient, with roots often associated with Roman gardens. European gardeners refined it during the Middle Ages, using flattened trees inside castle courtyards and along walls where open ground was limited. The French word originally referred to the supporting frame; over time, it came to describe both the method and the trained plant.
Common forms include horizontal cordons, fans, Belgian fences, and step-over designs. Pleaching usually involves weaving or interlocking branches into a hedge, while topiary shapes foliage into ornamental forms; neither is the precise answer here.