"Train the apples to the wall. Espalier"

Espalier
Creative Commons AttributionEspalier - Credit: Frank Paynter
"Espalier is the art of training trees to branch in formal patterns usually along a wall, or on a trellis. The technique of espalier first became popular several hundred years ago in the walled Medieval gardens of Europe. Few or no fruit trees could be grown in these walled gardens because of the limited space available. However, by placing the trees along the garden walls and training them to grow in a more or less two dimensional form, trees could be incorporated into the garden with relatively little loss in growing area."

- from Garden Line, The University of Saskatchewan