Pruning and Training Techniques for Young Apple Trees in the Slender Spindle Form

Pruning and Training Techniques for Young Apple Trees in the Slender Spindle Form

At present, the slender spindle tree form has become mainstream in newly planted apple growing areas. In developing the slender spindle form for apple trees, pruning and training during the young tree stage is a crucial part. Based on work experience in recent years, the author introduces the key technical points for pruning and training young apple trees in the slender spindle form as follows, to provide a reference for fruit growers (Figure 1).

Figure 1 Apple tree in the slender spindle form

1 Pruning and training in the year of planting

A mature apple tree in the slender spindle form has a height of about 3 m, an upright and strong central leader, a canopy diameter of about 1.5 m, a trunk height of about 60 cm, and about 30 small scaffold branches evenly distributed on the central leader, with branch angles of 90-110 degrees. The thickness of a scaffold branch is less than 1/3 of the thickness of the central leader at its point of attachment. Fruiting branches are distributed on the scaffold branches, with no distinction of lateral branches. Each scaffold branch is essentially a fruiting branch group growing horizontally to downward.

1.1 Developing a strong central leader

In the year of planting, head the trees back at different heights according to seedling quality. For seedlings 1-1.5 m tall, head back at a plump bud at 0.6-0.8 m; for seedlings 1.5-1.8 m tall, head at a height of 1.2 m; for seedlings over 1.8 m tall, do not head back, but remove branches thicker than 1/3 of the trunk; for seedlings less than 1 m tall, it is best to head back at a plump bud at 0.5 m and handle them in the second year. If the central leader grows into double or multiple leaders in summer after heading, select one vigorous branch as the extension leader and cut off the competing branches. To keep the central leader straight, a bamboo pole or steel pipe can be tied beside the tree to assist growth.

1.2 Developing small scaffold branches

Before budbreak in spring, notch the central leader every 5-6 buds, making cuts above the buds to promote branching on the central leader; more scaffold branches can slow the growth vigor of the branches. Remove branches on the trunk below 50 cm from the ground to reduce nutrient consumption. When scaffold branches are 20-30 cm long, use spreaders to open their angles to 90-110 degrees; open the angle wider for vigorously growing branches and narrower for weak ones. At intervals, bend and soften the scaffold branches once, and promptly twist any water sprouts on the upper side downward.

1.3 Bending branches, pinching and removing leaves

To control excessive extension of scaffold branches, pinch and remove leaves from scaffold branches longer than 60 cm: pinch off the tip of the branch, then remove 3-4 leaves while keeping the petioles. In mid-to-late July, twist the base of the branch with some force to make it droop slightly, controlling its growth vigor. In mid-to-late August, bend down any scaffold branches whose angles are not in place to ensure the branch angles are kept between 90 and 110 degrees. Generally, branches are bent to horizontal; overly thick and vigorous branches are bent to 110 degrees, in a slightly drooping state.

2 Pruning and training of second-year young trees

2.1 Spring branch treatment

Management of one-year-old branches on the central leader is the same as in the first year. Before budbreak, for horizontal branches that were twisted downward in July of the previous year, make spaced ring cuts on falsely vigorous branches and notch buds on vigorous branches; for buds on the upper side, notch behind the bud, and for side and lower buds, notch in front of the bud. Before budbreak, twist the branches downward and remove the terminal buds at the front to suppress the top and promote sprouting. For falsely vigorous small branches on horizontal branches, suppress the top and promote vigor for those within 15 cm long; for branches longer than 15 cm, twist again in the middle. Before and after budbreak, notch above buds in empty areas on the lower part of the central leader to promote short fruiting branches.

2.2 Maintaining the dominance of the central leader

Cut off scaffold branches thicker than 1/3 of the central leader and branches competing with the central leader. Keep as many branches growing from the central leader as possible. In summer, reasonably adjust the position and angle of scaffold branches so that they are rationally arranged on the trunk, spirally arranged according to space, without affecting each other.

2.3 Controlling the growth vigor of scaffold branches

Keep only fruiting branch groups on scaffold branches. When there are many water sprouts on scaffold branches, some can be appropriately thinned; when the remaining ones are 15-20 cm long, twist their bases and continuously bend and soften the branches. When horizontal small branches on scaffold branches are 15 cm long, pinch them to control length and promote vigor. In mid-to-late August, bend down the current year's scaffold branches, at the same angles as in the first year.

3 Pruning and training of third-year young trees

3.1 Continuing to maintain the dominance of the central leader

Cut off branches competing with the central leader so that the current year's extension shoot of the central leader grows more than 80 cm, and the tree height ultimately reaches about 3 m.

3.2 Controlling the growth vigor of scaffold branches

For thick, vigorous scaffold branches whose short-branch terminal buds sprout too early in early June, make ring cuts every 15-20 cm. Alternatively, spray 30-fold amino acids or the fruit tree regulator PBO to control growth vigor, promote the growth of many short branches, some of which may form flower buds.

3.3 Branch treatment

Pruning and management of one- and two-year-old branches on the trunk are the same as in the first and second years. For trees with a thicker central leader, make one ring cut around the trunk about 15 cm above the ground to control top vigor. After July, remove water sprouts in the inner canopy, dense upright branches and slender branches to save nutrients and improve ventilation and light conditions. In mid-to-late August, bend down the current year's scaffold branches, at the same angles as in the first and second years.

3.4 Promoting restraining branches on strong, vigorous scaffold branches

Before budbreak on strong, vigorous scaffold branches, leave 2 buds at the base and make ring cuts to promote restraining branches, diverting nutrients that the branch transports to the front end and slowing excessive vegetative growth caused by an overly vigorous front end. For branches thinner than a chopstick, make 1 ring cut; for branches thicker than a cigarette, make 2 ring cuts; for branches as thick as a little finger, make 3 ring cuts. The distance between cuts should be the width of a chive leaf.

After 3 years of pruning and training, newly planted young apple trees have basically formed the slender spindle form, with an obvious trunk and a tree height of about 3 m, on which about 30 small scaffold branches are evenly distributed. Scaffold branches longer than 70 cm should be trained to a slightly drooping state to control canopy expansion. Fruiting branch groups are borne directly on the scaffold branches. The difference between scaffold branches and the central leader is obvious, and some begin to bear flowers and fruit (Figures 2 and 3).

Figure 2 Blooming apple tree in the slender spindle form

Figure 3 Fruiting apple tree in the slender spindle form (Yangzhuang, Wu'an City)