Espalier ( or ) is the horticultural and ancient agricultural practice of controlling woody plant growth for the production of fruit, by pruning and tying branches to a frame. Plants are frequently shaped in formal patterns, flat against a structure such as a wall, fence, or trellis, and also plants which have been shaped in this way.
Espaliers, trained into flat two-dimensional forms, are used not only for decorative purposes, but also for gardens in which space is limited. In a temperate climate, espaliers may be trained next to a wall that can reflect more sunlight and retain heat overnight or orientated so that they absorb maximum sunlight by training them parallel to the equator. These two strategies allow the season to be extended so that fruit has more time to mature.
A restricted form of training consists of a central stem and a number of paired horizontal branches all trained in the same plane. The most important advantage is that of being able to increase the growth of a branch by training it vertically. Later, one can decrease growth while increasing fruit production by training it horizontally.
The word espalier is French, and it comes from the Italian spalliera, meaning "something to rest the shoulder (spalla) against." During the 17th Century, the word initially referred only to the actual trellis or frame on which such a plant was trained to grow, but over time it has come to be used to describe both the practice and the plants themselves.
Espalier as a technique seems to have started with the ancient Romans. In the Middle Ages the Europeans refined it into an art. The practice was popularly used in Europe to produce fruit inside the walls of a typical castle courtyard without interfering with the open space and to decorate solid walls by planting flattened trees near them. Vineyards have used the technique in the training of grapes for hundreds or perhaps even thousands of years.
A Belgian fence is created by cutting back an unbranched, slender tree to between fifteen and eighteen inches above the ground. The topmost three buds are allowed to form; one in the middle is trained vertically while two others are trained into a V shape. Any other buds are rubbed away. Removing the vertical stem completes the individual V-shaped espalier. By placing many similarly trained trees in a line two feet apart with their branches trained to the same plane, a Belgian fence is created.
The Belgian fence is an intermediary form that can then be used to train onward to many other forms of espalier, including: Step-over, where the branches are lowered down to the horizontal in autumn while still flexible enough and tied to a trellis; Fan, where the branches are lowered and cut back then trained further; Horizontal T, where the branches are trained to horizontal as with step-over but the vertical stem is trained up to another level and cut usually in spring of the second year, where another V shape is created and the resulting branches finally being lowered to another wire in autumn of the second year. Multiple levels of horizontal branching can be trained in this way.
Certain types of trees adapt better to this practice than others, but almost any woody plant can be trained to grow along a flat plane by removing growth outside that plane. Horizontal T training of an apple or pear tree is a good example of the ideal species for espalier. In the spring, the tree is pruned to the lowest wire perhaps 15 to 18 inches above the ground. During the summer, buds lengthen into branches; one trained vertically to the next wire while others are trained along the wires. Unnecessary buds are removed by rubbing them away with a thumb. In autumn, the side branches are lowered and tied to the wires completing the level. The following year another level is created.
Examples of species for espalier include:
Espalier design often uses traditional formal patterns developed over hundreds of years, but can also employ more modern informal designs. A stunted or deformed plant, or one that already has interesting or unique characteristics, might be just right for an informal espalier.
Common formal patterns include the following styles.
Espalier plants on solid walls are usually installed six to twelve inches from the base of that wall, to allow space below ground for roots to grow in all directions as well as space above ground for good air circulation and pest control. Supports for wire guides, which are generally necessary to train an espalier into a design, are installed first, directly into a wall constructed of suitable material. Masonry walls are ideal for placing U-bolts, eye bolts, or eye screws, anchored with either plastic plugs or expandable lead shields, directly into the mortar joints. Wooden walls may be better fitted with galvanized nipples, using turnbuckles for adjustment of the wire tautness.
Suitable, established and healthy plants, three to four feet tall and perhaps in three-gallon containers, are available from most nurseries. Some may even have trellises already installed. These plants could also be good candidates for espalier treatment if their form is similar to the intended design, as they frequently have already been pruned into a flattened overall plant shape. All that is required for such specimens is transplanting. Unpruned plants benefit from being allowed to become well established following transplant, before pruning them gradually into their flattened profile and training them as designed. Any major pruning needed is generally accomplished either while the plant is dormant or, for flowering plants, during the proper season for pruning that species. Bending and training of the limbs that will remain in the design is done during the progression of the summer season, when they are most flexible.