This type of tree emanated from France, and the name is simply a fanciful application of the French word cordon - a string or bell-rope - in allusion, presumably, to the fact that the tree is pruned in to a single stem, on which fruit hangs like a rope of Onions. We have several forms of cordon trees, e.g. single and double upright, and single and double horizontal; but in all the main principle is the same, namely, to restrict the tree to a formal shape and prevent its developing branches.
I have already shown how valuable the cordon system is where space is very scarce. It is so easy to err in forming cordons out of maiden trees that I am inclined to advise purchasing developed trees of three years old or upward. Several nurserymen make a speciality of them. It may be established with advantage as a general rule in managing cordons that as long a run as possible should be given to the head, with a view to providing a counterpoise to the severe restriction of the side growths. If a cordon tree is curtailed as to its leading shoot as well as to its side branches, it will dwindle and become unhealthy. This is particularly the case with horizontal cordons, which are useful for forming a low line of trees at the side of walks, in gardens where there is not room enough for the taller espaliers. Prune the side shoots both in summer and winter, at the former season to six good, well-developed, healthy leaves; at the latter season to within one or two buds of the main stem; but at all times and seasons give the leading shoot the utmost extension possible. In the case of low supports, a greater length of run may be secured by training upright trees diagonally.
The cordon system may be brought into play for arches, and a reference to Fig. 5, will show how the trees may be trained.
O, double horizontal cordon: a, end straining post and stay of trellis; b, upright post or standard, always between two trees; c, wire for securing cardons; d, stone earthenware edging to the walk; e, three years old double horizontal cordon Apple tree.
P, double trellis for training Pear trees: f, trellis; g, espalier or horizontally trained three years old trees; h, single vertical cordon trees.
Q, arch for training ornamental Crab Apples: i, trellis; j, double vertical cordon trees; k, walk.
R, wall wired for trees, either horizontal, fan, or cordon trained: l, wires: m. double oblique, cordon Pear trees - three years old.