Other tools and equipment include a soil sieve, a turntable, chopsticks, tweezers, a root hook, a trowel for smoothing the soil, and shears which you will use specifically for roots. Never use your good tools on the roots, since particles of soil and grit will certainly pit and dull them. Twine and tie wire, pliers, wire cutters, and moss for the surface of the soil to prevent erosion when watering are all helpful.
Herb Gustafson, on the Internet Bonsai Class, suggests advance planning including preparing your favorite beverage, being sure you have adequate lighting, and that you have plenty of time. Most importantly he says, “Remember to have fun.”
When to Repot
Repotting is best done, barring emergencies, in early spring just as the trees are ready to stir out of their winter dormancy. Why is this? An actively growing plant has tender white root tips which do the work of absorbing water and nutrients from the soil. These are easily damaged, which causes great stress to the plant. Therefore, we can reduce this stress by repotting when the plant is not actively growing. In addition, the rapidly approaching growing season assures that the tree can begin to heal any wounds caused by pruning of the roots and branch.
There are other times in our temperate climate during which growth slows down and repotting may be carefully carried out successfully. In the fall, as the plants begin to go dormant, trees may be repotted. However, the trees cannot regenerate the roots cut or heal the wounds they receive until the following spring. This can allow the onset of root rot and provide an opening for insects and disease. For this reason, spring is generally considered the best time to repot.
Why Repot?
Perhaps the most basic question of all is, why do we have to repot the tree at all? The answers arises from the very definition of bonsai : a tree planted in a pot. If you were to let the tree grow untouched in the same pot, within a few years the roots would fill the pot completely so that water and air would no longer circulate. Without water and air, the roots cannot take in nourishment, and the tree would certainly die.
The roots age much like the branches, and within a few years, only thick roots would be left with no room for feeder roots. Little by little the soil would become pulverized to dust which would not allow the passage of air, water, and nutrients. As has been stated before, the roots age much like the branches. So much so, in fact, that the roots have been said to be a mirror of the branches. Where there is an unusually strong branch, expect it to be directly over an unusually large root. If branches are long and without ramification, look for overlong roots. And if the leaves are withering and the branches are getting progressively weaker, look for a problem in the roots.
Repotting and root pruning, therefore, provide several benefits for the tree. Renewing the soil keeps air, water and nutrients available. Pruning the roots renews them and provides more of the active root hairs which do the work. It allows one to examine the roots for disease, infestation, rot, or abnormal growth. Finally, it allows one to improve the appearance of the rootage, and direct the growth of the rest of the tree.
Frequency of Repotting
The frequency of necessary repotting varies greatly with the species of the tree, its age in bonsai training, its apparent condition, and the results desired. Deciduous trees generally require repotting more often than evergreens, and young trees generally more often than mature ones. If the tree seems to be withering or declining in health, emergency repotting may be called for to correct root rot or infestation.
