When a tree, shrub or vine is trained to grow on a single plane and not allowed to deviate from it, that is known as the "espalier" style. The plane is often defined by a wall or fence. The plants are trained from the time that they are young on wires running along the wall or fence. The subsequent "espalier" is continually pruned thereafter, so that all its growth remains parallel to the wall or fence.
The trellis formed by the wire is sometimes itself referred to as "espalier."
Two of the reasons why espalier can be a useful technique in landscaping are:
- It can save space, which is important in landscaping small yards
- When installed along a wall with Southern exposure, the espalier-plants can enjoy a "microclimate."
Please consult my separate article for additional ideas for fence line landscaping.