Abstract
In soil-amending work to recover vigor of a weakened tree, pruning of root tips is usually prohibited by the arborists. On the other hand, in tea plant cultivation, productivity is recovered by renewing the roots by pruning root tips. In the soil-amending work to recover the vigor of an extremely weakened 130-year-old Japanese weeping-type flowering cherry at Tajimi City in Gifu Prefecture, which is a natural monument, we pruned the roots. Then, we examined the emergence, branching and elongation of new roots at intervals, to determine the suitable time of root pruning and suitable thickness of root to be pruned. The tree vigor after the root pruning observed in each above-ground organ was compared with that in a successor tree, and the effectiveness of root pruning was confirmed. In addition, we found that the growth promotion of each above-ground organ by root pruning was similar to that by cytokinin.
