Fresh, juicy lemons and fragrant blossoms are just two benefits of growing an espaliered lemon tree (Citrus limon) in your garden. An ancient method for growing trees against a vertical surface such as a wall, fence or wires between wooden posts, a tree trained as an espalier also provides structure in potager gardens, orchards and ornamental gardens. Hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11, a lemon tree can grow up to 25 feet tall, so select a compact variety to espalier. Create an informal structure, as a lemon tree's growth habit doesn't conform well to training into a regular pattern.
Screw a 1 1/2-inch eye screw 24 inches above the ground into a fence, post or other structure to support the lemon tree in a full-sun site with well-drained soil. Screw in another eye screw 24 inches above the ground and 4 feet along the fence, and another screw at the same height and 4 feet along from the second screw. This gives a line of three screws 24 inches above the ground and 8 feet wide. Screw an eye screw 18 inches above the first screw and another screw every 18 inches to a height of 6 feet 6 inches. Screw eye screws above the other two lowest screws every 18 inches to 6 feet 6 inches.
Thread galvanized steel wire through the three eye screws that are 24 inches above the ground. Fold the wire over and twist it together at one eye screw on an outer edge of the grid to secure it. Pull the wire tight through the eye screw at the other edge of the grid, and cut it with wire cutters to leave a 2-inch tail. Fold this tail in and twist it around to hold the wire in place. Thread and secure wire horizontally through the higher eye screws in the same way. Untwist and retighten wires as needed to create a taut framework.
Dig a hole with a spade 1 foot wider than the rootball of the lemon tree and to the rootball's depth in front of the center of the espalier support. Remove any covering from the rootball and place the tree in the hole so the surface of the rootball is level with the surrounding soil and the tree trunk is 6 to 8 inches from the base of the espalier support. Replace and firm soil at the base of the hole as needed so that the tree sits at the correct depth. Fill in the gaps around the rootball with dug soil and firm the soil gently with the heels of your hands. Water the lemon tree thoroughly.
Spread a 2- to 3-inch layer of organic mulch such as garden compost or leaf mold around the base of the lemon tree, avoiding the trunk.
Select three or four of the thickest vertical shoots on the lemon tree. Tie these shoots to the closest wires loosely with plant ties or garden twine at a 45-degree angle from the ground. Wipe the blades of pruning shears with rubbing alcohol, and prune all shoots thicker than your little finger where they join the rest of the tree. Tie side shoots horizontally to the closest wires and prune side shoots that aren't growing near wires where they join the tree.
Water the lemon tree regularly throughout the growing season so that the soil is consistently moist but never sodden, and top up the mulch when it thins out.
Tie the main lemon tree shoots to the wires as they reach them over the growing season, and tie side shoots along the wires horizontally.
Each spring, prune dead, diseased or overcrowded lemon tree shoots and those growing toward or away from the support or otherwise spoiling the shape of the espalier. Tie new shoots to the support, and prune shoots that grow beyond its edges.