A sunny, blank wall or a narrow garden is an ideal location for an espaliered tree. The practice of training fruit trees against warm south-facing walls was begun centuries ago. For extra frost protection the plant was sometimes attached to a hollow wall in which fires would be lit.
Almost any deciduous or evergreen tree or shrub with flexible branches — for example, forsythia, cotoneaster, viburnum, yew, or pyracantha — can be espaliered. Avoid woody plants with stiff, rigid, upright growth habits. Apple trees and crab apples are especially good to espalier.
To espalier an apple tree, stretch horizontal wires 18 inches apart along a wall. Plant a bare-root, one-year-old whip and head the top just below the bottom wire. From the emerging new shoots, select one to grow up to the next wire 18 inches above. Pick two side shoots to grow along the wire in each direction and tie them on. Rub off all other growth on the trunk and pinch shoots on the branches to keep them short.
During the first or second season, cut the main stem off just below the second wire from the bottom. This will initiate another set of buds, two of which should be kept for side branches and one for the trunk extension. Train these as for the first set. To make fruiting spurs on apples, cut back the lateral branches on the horizontal limbs to three buds. Continue training until three wires, or more if desired, are covered with branches. When the tree reaches the top wire, eliminate the trunk extension by heading it, and retain the two side branches.
For extra convenience, make a wood or wire trellis and attach it to a wall with hinges at the base and hooks on top. When painting the wall, unhook the top of the trellis and carefully lean the espaliered plant, trellis and all, away from the building until the paint is dry.
Regular pruning is necessary during the growing season to restrict plants to a single flat plane. Use thinning cuts rather than heading cuts in this summer pruning.