Key Technical Points for Summer Training and Pruning of Cherry Trees

Pinching is the most widely used method in summer pruning of cherry trees; it refers to removing the tender shoot tip before the new shoot has become lignified. Pinching young trees encourages more shoots to sprout, lowers the position where shoots emerge, rapidly increases the number of branches and leaves, expands the canopy, reduces ineffective growth, and promotes flower bud formation. Pinching trees in the early fruiting stage and the full fruiting stage can save nutrients, increase the fruit set rate and fruit quality, improve the quality of flower bud formation, reduce vegetative growth, and prevent the fruiting position from moving outward. Pinching can be divided into light pinching, moderate pinching, and heavy pinching. Light pinching removes only about 5 cm from the tip; after pinching, only 1-2 new shoots sprout and extend, and with continuous light pinching and a growth amount of 10-20 cm, fruiting branches can be formed. The purpose of moderate pinching is to promote multiple branches; it must wait until the new shoot has grown to more than 40 cm, then remove more than 15 cm, which generally can sprout 3-4 branches. Heavy pinching: when the branch has developed to more than 40 cm, leave about 15 cm and pinch, which can not only promote branching but also cause the lower buds to sprout and grow into short branches or leaf cluster branches, forming small fruiting branch groups. The length of the branch left after pinching should be determined according to the space where the branch grows and the different uses of the branch. Generally, if it is used as a scaffold branch, a longer branch is left. When the new shoot has grown longer but the retained branch is shorter, and the pinching site has already become semi-lignified, pruning shears must be used, which is called shoot tip pruning. Shoot tip pruning has a stronger effect than pinching.

Cherry fruit ripens early, and after harvest the tree body has no load; apart from nutrients needed for flower bud formation, the rest is used for vegetative growth of the tree, and the growth vigor is relatively strong, making it easy to produce some water sprouts and upright new shoots. In particular, after pinching some branches, because of the early maturity of their buds and the stimulating effect of pinching, 3-5 or even more new branches will be produced, some of which grow in unsuitable positions but have space around them, so twisting shoots is needed to change the growth direction of these branches, regulate growth vigor, and make full use of space. Therefore, shoot twisting is an important method for summer tree management and training and pruning of cherries. Compared with the branch twisting of peaches and apricots, the operation position for cherry tree shoot twisting is slightly higher, so it is called shoot twisting. The operation method is to hold the middle-lower part of the new shoot with the hand when it is semi-lignified and twist it in the opposite direction 180 degrees, so that the new shoot is horizontal or drooping, injuring the wood and cortex but not breaking them. Twisting shoots in May-June is beneficial to flower bud formation. Twisting shoots on back branches and inward-facing branches can effectively weaken growth vigor and increase the number of small branches. The timing of shoot twisting must be grasped well; if twisted too early, the new shoot is tender and not yet lignified, and is easy to break. If twisted too late, the new shoot has already lignified, the cortex and xylem are easy to separate, and it is also easy to break, often causing death from the twisted site.