Caring for your Bonsai tree involves many of the same activities associated with caring for a pot plant or an indoor plant. Well developed and healthy fibrous roots are essential for the continued good health of your Bonsai tree and repotting is an essential way to manage this process. Normally a young or fast-growing Bonsai will need to be repotted roughly once a year; for less prolific growers or older trees, it can be done as infrequently as once every five years. You should always try to re-pot during late winter or early spring when the buds start to swell.
The process of repotting a Bonsai tree is one that you should take seriously and follow these simple instructions:
First, you should tidy the tree by carefully pruning off any unwanted, long branches. Also, make sure the tree has been undercover for a few weeks if it is an outdoor Bonsai, this way the soil will be relatively dry. Once you remove the tree from its pot you will be able to see whether it really needs repotting. If it is root bound then you should re-pot it, however, if there are another few inches of room so the roots can grow a little longer then you can carefully replace the tree in its original pot and continue as normal.
You should remove surface soil from the roots either by hand or using a nylon scrubbing brush. Brush away from the trunk and be careful not to damage any of the roots. Removing the loose soil will give the Bonsai tree a healthier look and feel. Once you’ve removed most of the soil in this way, you can use a small, fine bristled paintbrush to remove the soil stuck in the roots or that has collected in the roots.
Use a Bonsai fork to comb out the roots. Do this by combing out the roots from underneath and then use scissors to prune up to a third of the roots and then cut out small wedges around the root base to allow fresh soil to collect and keep your Bonsai healthy. Add a layer of grit to the bottom of the pot and then add the Bonsai compost of your choice.
Take the time to position your Bonsai tree in the pot and then push a little more soil into awkward places. Complete this as often as you need to as mentioned above.