When is the best time to repot and how should I do it?
> Potting is one of the most complicated subjects in bonsai.
> Many newcomers to the hobby make the mistake of putting a tree into a bonsai pot before it's ready.
> If you are putting a tree into a training pot and are not going to root prune you can slip pot just about anything most of the time. This is simply placing the root ball in another pot which may or may not be larger.
> Root pruning and repotting a root bound plant will refresh it and cause it to put out fresh growth.
> Once again you must know what type of tree you have. Some trees grow so fast they must be root pruned and repotted yearly. Others may need it every other year or some exceptionally slow growers every 3-5 years.
> Generally, tropicals are best repotted and root pruned during the hottest part of the year when they are actively growing.
> Repot most temperate climate woody trees just before bud break or when they first start showing fresh white root growth. Usually this is accomplished in the early spring. Some species can also be repotted in late fall.
> When repotting a finished bonsai, the general practice is to remove one half to two thirds of the old soil and prune one third to one half of the roots. The tree is then replaced in the same pot.
> You should prune foliage from the tree when you remove roots. Pruning a comparable amount will save stress on the tree. For example, if you remove 1/3 of the roots, top prune 1/3 of the foliage.
> It may be easier to prune the foliage while the tree is still in its pot.
> Have everything you need at hand before you begin, tools, soil, pot, screen and wire.
> Do not do this in the bright sun light or the roots may dry out.
> Pull the plant out of the pot and attempt to untangle the roots. Some people use a root comb or even a fork will do.
> The roots should be trimmed all around so the tree will fit back in the container with fresh potting mix. Try to spare as many of the small, fine roots as you can. These smaller roots are more efficient at taking up water that the tree will need after the pruning.
> Place a shallow layer of fresh soil in the bottom of the pot and set the root ball on it. Pour more soil around the roots, tamping it into place.
> Check the soil for air pockets. It can sometimes be hard to get soil to fill all crevices between the roots. One method is to manipulate a chopstick or wooden skewer between the roots to make the soil spill down.
> If you did not cut back the foliage yet, do so now.
> Water the tree thoroughly. This will settle the tree into the new soil.
> The tree should be anchored in the pot some way so that the wind does not move it around in the soil.
> The tree should be placed in a semi-shaded location for two weeks.
> Do not ferilize until you see new growth.