How to prune fruit tree bonsai? A full analysis of the technical key points

  Fruit trees grown in pots put on a relatively large amount of growth each year, and if left to grow unchecked, their fruiting is also hard to control. To maintain a perfect, compact tree shape and effectively control growth and fruiting, pruning must be carried out several times a year. By pruning period, it can be divided into dormant-season pruning (winter pruning) and growing-season pruning (summer pruning).

  Fruit trees can be pruned both during the dormant season and the growing season, but pruning at different times has different tasks.

  Dormant-season pruning, that is, winter pruning, is carried out from after normal leaf fall in autumn to before bud break the following year. At this time, the tree's stored nutrients have already moved from the branches and leaves to the branches and roots, and have been stored away. Pruning at this time causes relatively little loss of nutrients, and because there are no leaves, it is easy to analyse the tree's structure and its pruning response. Therefore, winter pruning is the main pruning period for most fruit trees; but there are exceptions. For example, pruning walnut trees during the dormant season causes bleeding, so pruning must be carried out before leaf fall in autumn or after bud break in spring and before flowering; grapes also have a bleeding period before bud break, and pruning must avoid this period.

  The main training and pruning tasks to be completed in winter pruning are: developing scaffold branches, balancing tree vigour, adjusting subordinate relationships, developing fruiting branch groups, controlling auxiliary branches, promoting the growth of certain branches or the formation of flower buds, controlling branch quantity, regulating the ratio of vegetative branches to fruiting branches and the number of flower buds, and controlling the size and density of the canopy; improving light conditions inside the canopy, as well as renewal pruning of ageing trees.

  Growing-season pruning is carried out in three seasons: spring, summer and autumn. Spring pruning, carried out from after bud break in spring to before flowering, is further divided into pre-flowering follow-up pruning and late pruning. Pre-flowering follow-up pruning is a review and supplement to the winter pruning task, mainly to further regulate growth vigour and flower quantity. For example, when apple flower buds are hard to identify, one can deliberately leave more "flower buds" during winter pruning, then carry out a follow-up pruning from flower-bud swelling to before flowering, thinning out excess flower buds and cutting back overlong branch groups; this helps control flower quantity, improve fruit set and develop fruiting branch groups. Before and after bud break on young trees, widen the opening angle of auxiliary branches and carry out girdling at the same time, to increase the bud break rate and increase branch quantity, which helps young trees fruit early. Late pruning refers to cutting back after bud break on cultivars with a low bud break rate and poor branching ability, removing the parts that have already sprouted. This "late pruning" measure has the effect of raising the bud break rate, increasing branch quantity and weakening apical dominance, and is a commonly used technique for getting young trees to fruit early.

  Summer is a period of vigorous growth for fruit trees and also a good time to control excessive growth. Many fruit trees use summer pruning to control branch vigour and reduce nutrient consumption, so as to moderate tree vigour, promote flower bud formation and improve fruit set; it can also improve light conditions inside the canopy and improve fruit quality. Commonly used measures include propping branches open to widen angles, pinching and thinning branches, bending branches and twisting shoots. Girdling and scoring, etc., are indispensable technical measures for young grape, peach and apple trees.

  Pruning overly vigorous trees before leaf fall in autumn can help control tree vigour and restrain excessive branch growth. At this time, thinning out large branches and cutting back causes less local stimulation, and is often used for tree species and cultivars that are sensitive in their pruning response. Cutting off the immature or poorly lignified parts of new shoots in autumn can help fruit trees enter dormancy early, which is beneficial for young trees to overwinter. Growing-season pruning loses more nutrients and can also reduce the current year's growth, so pruning should not be too heavy, to avoid weakening tree vigour excessively.

  In short, pruning at different times each has its own characteristics, and in practice they should be coordinated and applied together according to the specific situation. At present, production often only emphasises winter pruning while neglecting growing-season pruning, which is wrong.