I would say the most important task in bonsai is root development, rune pruning, or repotting. The trees energy is supported by the roots. A bonsai must have healthy fine roots to become a good bonsai which will lead to a healthy tree and eventually withstand the other training that follows to create a good bonsai. I was lucky enough to learn a systematic method of repotting from Boon Manakitivipart when I took his intensive class. Boon is very methodical and meticulous about how he did everything and it shows on his trees. I will do my best to walk you through what I do following what I best remember from that intensive class. I’m doing this on one of my largest trees the Viburnum which I’ve written a few times here. The method will be similar to smaller trees except the soil particles may need to vary. Of course the timing of everything is critical which you’ll need to learn for every tree. For deciduous trees, it is best to do it while they are dormant but also be watchful of freezing. I’m trying to do this as early as possible because I have a few that I have to do and don’t want to get behind before I get too busy. I did the repotting mid January.
I started setting up the repotting in the morning but was interrupted to visit a family at the hospital and returned to finish the project in the evening. I took the photos in the morning and when it came time for the dirty work, I solicited my 8 year old daughter to be my photographer. She did a good job.
Why I repotted this tree: 1) Last years growth was weak even when I fertilized more. I suspected the pot is full of roots that nutrients maybe are not getting into the roots. Tip for finding out if a tree needs to be repotted: use a wooden chopstick to push thru the soil, if it’s had to push, the pot is full of roots. 2) The existing pot that is in is unglazed and wanted a glazed pot that is more suitable for deciduous trees. I wanted a similar shape and almost the same size to match the proportions and least root ball shape changes.
Instead of showing a series of photos here on this blog (which would have taken up all of my free data space for this blog). I created a video/slide show instead. I don’t have the proper video editing program so it took me more time to do it but it is worth sharing this since. Caution: This repotting is for my tree and specific for my tree, consult with a bonsai professional in your area when you do yours. The techniques will be similar but timing for each tree, soil mix, and after care may vary.