Growing trees into an arch is an art form that goes back for centuries. Essentially a form of espalier, arched forms were embraced by the Victorians. Today's gardener, however, has the advantage of new tree forms including columnar apple trees. Columnar apple trees do not require pruning, naturally growing short fruiting spurs. With patience, a metal trellis and plant ties, a gardener can quickly train two columnar apple trees into an arch.
Install any hardscape, such as paths or fences, before planting the trees. Walkways are generally 3 to 4 feet wide.
Assemble the metal trellis according to the package instructions. Push into the ground so the trellis arches over each side of the walk.
Dig the planting holes just outside of the trellis, a little deeper and twice as wide as the root balls. Fill with water and allow to soak into the soil before continuing. Do not amend the excavated soil.
Slide the trees out of the grower's pots. If planting bare-root trees, remove the wrappings and soak the roots in a bucket of water for at least an hour to rehydrate the trees. Unwind any tangled or encircling roots. Trim any broken or decayed roots.
Place the trees in the planting holes at the same depth as in the pot, gently spreading the roots over the soil. Backfill with the excavated soil and tamp firmly. Water thoroughly.
Cover the exposed soil with 3 inches of mulch, pulling 4 inches back from the tree trunks.
Attach the trees to the trellis using plant ties. Do not prune the leaders or main stems. As the trees grow, continue tying to the metal trellis so they arch over the path.
Water regularly until established, then water once a week.
Fertilise with a balanced 10-10-10 fertiliser according to the manufacturer's instructions.
Consult with the local cooperative extension office for information on fruit trees that thrive in your area. Columnar trees generally do not need pruning. They fruit on short spurs along the trunks. The inexpensive metal trellises found in discount stores are 15 to 18 inches wide. As columnar apple trees are only 18 inches wide, plant two trees on each side if a heavier canopy is desired. Plant two different varieties for better pollination of the trees. Other dwarf fruit trees are suitable substitutes, however, they will require pruning to shape and maintain the arched form.
Cover the trees if a severe frost or freezing weather is forecast. Loosen the plant ties as the trunks thicken; do not strangle the trees. The inexpensive metal trellises eventually rust, however, the trees should be self-supporting in three or four years. Monitor the trees for pests and disease.