Detailed Explanation of the Method for Cultivating Chinese Chestnut Trees in an Open-Center Tree Shape

The low-trunk, short-crown, multi-main-branch open-center tree shape for Chinese chestnut (Castanea mollissima) is especially suitable for wide-row, short-dense planting on steep terrain such as mountains and hills. So, how do you master the key points of the shaping technique? Recently, a reporter interviewed Tian Shoule, a researcher at the Shandong Institute of Pomology.

Trunk determination For a current-year grafted seedling, when the new shoot growing from the scion reaches 30-40 cm, pinch off the growing tip to determine the trunk; for a directly planted grafted seedling, cut it back at 30-40 cm above the ground, leaving 2-3 plump buds below the cut, and after determining the trunk, promote the growth of robust branches to facilitate shaping.

Selecting and retaining main branches In the year the trunk is determined, select an upright vigorous shoot from the newly sprouted shoots as the trunk extension shoot, and at the same time select 2 relatively thick, slanting shoots in the lower part as the first and second main branches, with the lowest main branch as the first main branch, arranged upward in sequence. When the trunk extension shoot grows to 30-40 cm, pinch it again. From the robust shoots sprouting after the second pinching, select 2 slanting shoots as the third and fourth main branches, and note that the third and fourth main branches should be staggered in distribution with the first and second main branches to avoid overlapping. The trunk extension shoot continues to grow upward and is no longer pinched. If the number of main branches in that year cannot reach the reserved number, then in the second year cut back the trunk extension shoot and select main branches again from the newly promoted shoots.

Selecting and arranging side branches After branch bending in early spring, the main branches will sprout a large number of lateral shoots. From the robust branches of the main branches, select and arrange reasonable side branches. The first side branch is 50-60 cm from the trunk, obtained by selecting naturally sprouted shoots or by notch budding. For the other side branches that sprout, retain 1 every 20-30 cm, and as far as possible retain lateral shoots with an open basal angle, or widen the basal angle by methods such as branch bending and propping, with the basal angle of side branches generally greater than that of the main branches. Pinch some vigorously growing side branches to directly train them into fruiting branch groups.

Training fruiting branch groups In the second year's winter pruning, lightly cut back the first to third main branches, removing 1/3 of the current year's shoot length; lightly or moderately cut back the fourth and fifth main branches, removing 1/3-1/2 of the current year's shoot length. For the first to third main branches, select and retain 2-3 side branches, with the first side branch about 60 cm from the second side branch, and the second side branch about 50 cm from the third side branch, and remove all the remaining side branches. For the fourth and fifth main branches, select and retain the 1st-2nd side branches, with a side branch spacing of about 50 cm, and remove all the remaining side branches. Prune the retained side branches, making a light cutback at a plump bud of the extension tip to promote branching and form fruiting branch groups. For fruiting branch groups that have already formed, retain 8-10 fruiting branches per square meter, and at the same time heavily cut back some vegetative shoots to cultivate fruiting mother branches for the next year. After 3-5 years of shaping and pruning, the low-trunk, short-crown, multi-main-branch open-center tree shape is basically formed.