Repotting Bonsai
An essential element in ensuring that your bonsai tree remains healthy is root pruning. This is carried out as part of the process of repotting bonsai.
In nature the roots of trees spread as they grow and form new roots. This pattern is not possible in a bonsai confined to a small pot and that is why root pruning and repotting are so important.
Root pruning has the effect of encouraging the development of fine feeder roots that are essential for the uptake of nutrients and water. This ensures that the tree remains healthy and less susceptible to disease.
The frequency of repotting depends on several factors. These include the age of the tree, the species and the size of the pot. The best time to repot bonsai is in the spring, just as the roots start to grow. This minimises the amount of stress that the tree will experience.
Gently ease the tree out of the pot and loosen the roots with your hand or an implement like a chopstick. Remove the soil from around the roots.
If there are any thick roots these should be cut back as far as possible. Then use sharp shears or scissors to cut off the finer roots. The bottom of the roots should be flat after cutting so that air pockets do not form when repotting.
Removing air pockets after repotting
The new pot (or the existing pot once washed) should be prepared by placing mesh over the drainage holes and inserting some wire to secure the root ball. Place a layer of soil in the base with a small mound underneath the tree.
Position the tree with the right orientation, secure with wire and then fill with soil to just below the pot rim. Gently move the soil around the roots with your fingers (some use a chopstick) to ensure that there are no air pockets. This need to be done carefully to avoid damaging the roots. Water the tree well.
For about 4 weeks after repotting keep the bonsai tree out of the sun and wind and don’t fertilise. When new growth appears the tree can be fertilised and brought back into the sun.
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