Cordon training is an old method used for growing Apples and Pears. It is the easiest pruning method there is and, as the trees can be planted at close proximity and are productive, it has stood the test of time and remains of the most popular growth forms today.
Planting can be just 2.5' between trees and, whilst once they were planted at a 45 degree angle, nowadays they are often planted vertically which takes up less space. These trees are ideal for walls, post and wire support system, used to segregate the garden as a 'fence', on allotments or they may be grown in containers.
Two cautions: avoid tip bearing varieties such as Worcester Pearmain, which won't yield well pruned as cordons. And light soils do not support cordons very well; it would need improving with plenty of organic matter. That aside these would be my first recommendation for smaller gardens and gardeners new to fruit tree cultivation.
Cordon fruit trees are in fruit the second season after planting and in heavy crop in 4 years. It is possible to grow a large range of varieties in a very small space to ensure excellent pollination and a full season long crop.
PLANTING AND SUPPORT. Space the cordons 2 feet 6 inches apart when planting in rows 6 feet apart with the rows running north to south, if possible but this is not essential. A wall or fence is suitable for growing cordons or they be grown in the open garden on a wire fence. Drive in the posts to about 2ft deep every 12ft, to hold the support wires. These should be spaced 2ft, 4ft and 6ft high using gauge 10 to 12 wire. Bamboo canes 8ft long should then be tied to the wires at an angle of 45 degrees with the tops pointing towards the north if grown north/south or the east if growing east/west. Space the canes at one for each tree planted, when planting the trees they should be planted 9 inches away from the structure to allow room for trunk growth. Plant an angle 45 degrees with the scion above ground and facing upwards, the trees should then be tied securely to the cane using thick, soft string or chain lock plastic ties.
PRUNING THE CORDON TREE. Every Summer at the stage of growth previously described, all of the laterals that are growing from the main stem should be pruned to leave 3 to 4 leaves. Do not prune those less than 9 inches long as these may have fruit buds.
All sub laterals (shoots which grow from previous laterals) should be pruned back to two leaves. If secondary growth occurs in poor growing seasons, prune back to one bud from your earlier Summer pruning in September. All of this may sound drastic and complicated but it is not, it is essential and easy, so easy in fact that it has been known in large areas of professional trials to Summer prune with hedging shears. We ourselves still prefer the traditional method!