Root pruning is a technique that is essential for maintaining the health and appearance of bonsai trees. Root pruning involves removing some of the roots of the bonsai tree when repotting it, to prevent the roots from becoming overcrowded and suffocating the tree. Root pruning also stimulates the growth of finer roots that can absorb more water and nutrients, and reduces the vigor of the tree so that it can grow in a small pot. Root pruning is usually done in late winter or early spring, before the tree starts to bud. To root prune a bonsai tree, one needs to carefully remove the tree from the pot, comb out the roots with a root hook, and cut off any thick, long, or damaged roots with sharp scissors. The amount of roots to be removed depends on the species and age of the tree, but generally one should aim to balance the roots with the foliage. After root pruning, the tree should be repotted in fresh soil and watered well. Root pruning is a delicate process that requires skill and patience, but it is vital for creating beautiful and healthy bonsai trees.