Repotting is nearly over for most species of trees now that Spring is finally here and hopefully all your trees are doing well. Lots of activity has been going on behind the scenes for everyone who owns a bonsai as it is a busy season ensuring that all your trees requiring repotting are carefully repotted. One of our Club members bought in a Korean Hornbeam to demonstrate his repotting technique and here are a few images of the process.
The first step is to remove the tree from the pot and this begins with cutting the wires beneath the pot that aid with holding the tree in the pot using wire cutters.
Step two is to carefully run a blunt flat edged tool around the inner edge of the pot to release the roots from the side of the pot and aid with levering the root plate out of the pot. If the bonsai pot has an inner lip then this can make removal of the root plate more difficult during this process so choose carefully on your pot choice to avoid pots with inner lips where possible.
Step three is to carefully lift the tree and root plate from the pot and move the pot away for the time being. This may require more than one person subject to how large the tree is and how easy it is to remove from the pot. In this instance it was a two person activity due to the size and weight of the tree.
Step four carefully tease out the roots and remove the old soil from the root plate. Depending on the stage of the development of the root pad / plate the extend of soil removal varies. This example was to demonstrate that not all the old soil was removed but the majority of the edge of the root plate soil was removed to enable new soil to be replaced around the root tips. Once the roots are free from soil, any adjustments to the root pad can be made through pruning. As this is a well developed and established root plate, only minor root pruning was required to trim off the longer roots back in line with the root pad.
Step five, re-secure the tree in the pot after cleaning the pot. Set the wires up again to tie the tree in and various techniques can be used. Once the tree is tied in securely, start to add the new soil, in this case it was sieved akadama. A chop stick was used to aid with pressing down the granules between the roots and filling all the available space within the pot and this reduces the damage to the roots if done carefully. Tap the sides of the pot to aid with settling the granular soil and add until the required soil height is reached and all the roots are covered.
Ensure that once you finish repotting; water the soil thoroughly. This ensures the roots are kept moist and importantly removes any remaining dust is washed out from the soil. Keep the tree in a shaded or semi-shaded position, out of the cold or exposed environment for a few weeks after repotting, to allow the tree time to adjust. This reduces the stress of the activity on the tree.