The form, and even the plant, you choose depends on your objectives, your garden's site conditions, and your level of patience for the pruning and training that an espalier requires. Dwarf pear and apple trees, which work well for formal shapes, need at least 6 hours of sun a day and a careful hand to avoid lopping off the thickened growths, called spurs, from which fruit develops. Certain ornamentals with flexible branches—flowering camellias and pyracantha, to name two—not only may thrive in shadier spots but also lend themselves to looser, free-form designs more forgiving of mistakes. At its most basic, an espalier may consist of vines, such as ivy or wisteria, that are tied up and coaxed to grow in particular patterns or directions.
Shown: This tree is trained into a fan shape.