Effects of heading back pruning on the bearing habit of Japanese chestnut [Castanea crenata] tree: Of the branches bearing no catkins in the previous year

Effects of heading back pruning on the bearing habit of Japanese chestnut cv. Tanzawa were studied for a better understanding of formation and development of female flowers. Vegetative shoots on two-years-old trees which had borne no catkins in the previous year were used. Results obtained are as follows. The number of unisexual male catkins per shoot which bore male catkins, as well as the rate of shoot which bore male catkins were higher, as the position of the shoot was closer to the terminal end on the fruit bearing branch. Effects of heading back pruning itself were, however, nonsignificant. The number of male catkins per branch was considerably decreased by heading back pruning. The number of bisexual catkins per shoot which bore bisexual catkins was considerably increased by heading back pruning, when compared to the control of the same position. The rate of shoot which bore bisexual catkins showed a tendency similar to the number of bisexual catkins. The number of female flowers per bisexual catkin which developed female flowers was doubled by heading back pruning, when compared with the control shoot of the same position on the branch. As a consequence, the disparity in the number of female flowers between heading back pruning and non-pruning was greater than that of bisexual catkins. Unlike unisexual male catkins, the number of female flowers per branch was not decreased much by heading back pruning. Thus, heading back pruning from 10 to 15 buds resulted in bearing about the same number of female flowers per branch as non-pruning. Heading back pruning resulted in longer shoot which grew on terminal parts of the branch and larger leaf area of the shoot. Though the number of burs per branch was decreased by heading back pruning, the number of nuts per bur and the weight per nut were increased making up for the decrease. Both nut weight power bur and nut yield per branch were, therefore, improved