Key Points of Winter Pruning Techniques for London Plane

London plane, commonly known as plane tree, is a large deciduous tree that can reach 30 m in height. It is a famous shade tree and street tree species, cultivated throughout China, generally used as a street tree.

Winter shaping and pruning have an important effect on the growth and tree form of London plane. Without timely and reasonable winter pruning, the tree form will become chaotic, with long main branches, few leaves or low bushy growth, greatly reducing its ornamental value and shading effect. Timely and reasonable pruning can, within a short period, give the tree a majestic, upright, tall and graceful form, with branches well-spaced and orderly, many well-proportioned lateral branches, dense dark green foliage, and enhanced natural immunity of the tree.

Winter shaping and pruning of London plane can be carried out from the time the leaves fall in autumn and winter, the soil freezes and the tree enters dormancy until the sap begins to flow in the following spring. For newly planted young trees, when the trunk height reaches 2.5 to 3 m, it is cut back, which is called "trunk establishment." Pruning can be done on the basis of an overall view of the whole tree and a decision on the future training direction: first cut upright branches and drooping branches, then cut diseased and pest-infested branches, crossing branches, thin and weak branches, inward-growing branches and branches affecting traffic facilities, and finally retain 3 to 4 strong main branches. The retained main branches should be favorable for future shaping, with strong growth and moderate spreading angles. After selecting the main branches, cut them back 30 to 40 cm from the base, with smooth cuts that do not damage the bark, and apply a wound-protection agent to the cuts to prevent pest and disease attack and water transpiration. Smoothing the wounds also promotes the formation of callus tissue, helps wound healing and prevents infection by pathogens. Wound-protection agents can be grafting wax, whitewash, tung oil or paint.

Every 3 to 4 years of growth, young trees should undergo a major trunk cutback in winter. Generally, the 3 to 4 main branches retained the first time can remain basically unchanged, and 1 to 2 strong small branches are retained on each main branch, cut back to a length of 20 to 30 cm. The lateral branches on the small branches can be retained according to the specific situation. If, for example, the communication lines beside the tree are not high, it is also acceptable to retain only the 3 to 4 cut-back main branches left at the first trunk establishment; this can reduce the height of the whole tree and at the same time increase the light penetration through the branches and leaves, neither affecting its growth nor failing to maintain the tree form well.

For London planes that have already taken shape, a comprehensive pruning should also be carried out every winter. Pay attention to developing the dominance of the main branches, and cut off diseased and pest-infested branches, upright branches, overlapping branches, excessively dense bushy branches and lateral branches. Cut back overlong main branches to stimulate the main and lateral branches to sprout branches and leaves from their bases, prevent bareness, and ensure a relatively thick leaf canopy layer.

London plane has strong sprouting ability and is very tolerant of pruning. If pruning is reasonable, the tree's graceful appearance can be maintained; if pruning is unreasonable, it can also be remedied in time at the next pruning to achieve the proper tree form effect.