Great question. A number of the Bonsai Shinshi videos are filmed at a friend’s workshop in Japan (Daisaku Nomoto). We talked about the difference in approach to repotting pines and other conifers. Some key takeaways:
- When trees are well-suited to the local weather, it’s easier for them to recover after repotting.
- Removing lots of roots and/or soil is possible but not always advisable depending on the care it gets afterwards. If the weather and watering is perfect, it’s much easier for a tree to regain its strength after a growing season or two.
- Little to no work is done after extensive repottings. This lets trees recover their strength before they are worked on again.
- The soil mix is also different. In the US, mixes with up to 1/3 akadama are popular where mixes up to 60-80% akadama are popular in Japan.
I occasionally repot conifers as they do in this video but I don’t typically recommend it as it requires that the trees are healthy to start with and receive good care - and rest - afterwards.
I also repot trees out of season. We can repot most trees most days of the year, but the extent of the rootwork will determine how well the tree recovers afterwards. I’ve had good results with repotting pines at decandling time, but I was sure to water lots in the following months - the time of year when Japan experiences heavy rain and high humidity.