Fig. 1 Belgian fence illustration by Beth Thevenot

A Belgian fence is a style of espalier in which limbs are trained into a lattice-like pattern. Identical varieties of fruit can be used or even a mix of cultivars, i.e. the annona family.
Select trees or whips with ½" to ¾" caliper trunks and set them against guy wires or hogwire attached to a frame to support the trees while training them into place. The best time to start an espalier is several weeks before the tree breaks dormancy in late winter or early spring because the plant will have a more vigorous response to the pruning cuts made after planting. The technique can also be done in cooler fall temperatures.
A full-fledged fence can be developed in three to four seasons. Whether 6 ft. long or 60 ft. long, the process will be similar.

Materials (for a six foot Belgian fence):

    6 trees of ½" to ¾" caliper, preferably grown on dwarf or semi-dwarf stock
Two 4" x 4" cedar posts
Eight feet of hogwire or other agricultural fencing

Tools:

Hammer
Table saw with Dado Blade
Electric drill
Nails and screws
Blue plastic tape
Gridded paper
Pencil

Directions

1. Select a site where trees will receive a full day's sun. Amend soil as needed.

2. If using hogwire/fencing, use table saw and dado blade to cut notch lengthwise on the posts, centered on the interior sides of the post.

3. To make freestanding fence, erect support grid of posts and wire. Field fencing or hog wire can be set between posts set into gravel 8 feet apart. After installing posts, set hogwire into dado and screw into place with stainless steel screws. Guide wires can also be used with turnbuckles if preferred. The grid of hogwire helps to map out the design.

Trees can also be trained on an already existing fence, although unless it is chain link, attach turnbuckles to extend eight inches out from fence to provide air circulation for trees.

4. Draw out design on gridded paper. The traditional design of Belgian fences involves trees planted 18 inches on center with a pattern of branches angling off at 45 degree angle from the base of the trunks about 16 inches from the ground. The ending trees of the fence will have one branch angled at 45 degrees towards the rest of Belgian fence with the other branch being trained perpendicular to ground. Pattern should resemble an argyle sweater with lines coming down from the base of the bottom of diamonds.

5. Using plastic tape, set out design on hogwire or fence, starting with first tree one foot in from cedar post and ending one foot before other post with final tree. Set trees in place and plant trees, ideally setting trees in so dormant buds are at point where tape steps off from 90 degrees to the first 45 degree angle. Water in plants.

6. Look at buds on tree to decide where to cut. Look for outward facing buds that are already pointing in the right direction at or slightly above spot where pattern on fence angles off. Cut each tree with sharp pruning shears above chosen buds. This will trigger tree to restart or branch at desired place. Never cut below first six inches of main stem as most trees are grafted and the tree won't come true to its variety of cut below bottom bud union or graft.

7. Tie main stem to support fence. In about three to four weeks, buds will grow on. Point new stems in desired direction of pattern and tie them on the support when they are about six inches long. End pieces will have one piece going up at 90 degrees and the other stem at 45 degrees. Interior trees will have each branch trained up at 45 degrees in each direction. Continue to tie in stems as they grow on along tape lines.

Fig. 2

Belgian fence close-up 

Fig. 3

Circular Belgian fence 

Fig. 4

Belgian fence