I was going over my documentation from the past 6 to 7 years and thought that talking about treating the wounds on a bonsai trunk could be an interesting subject for my first blog post. In Japan, a healed wound is a sign of age. With some trees, in time, there is a layer of bark forming on the callus tissue. The ideal end result is a tapered trunk, with no visible signs of the work that was done over the years. Another advantage of closing up all the wounds is keeping the tree in better health for many years and preventing the xylem from rotting.
The basic method of closing up a wound is to make a clean smooth cut and use cut paste immediately after. The smooth surface helps the callus to slide over the xylem and the cut paste keeps the area moist and vital to help the tree form the initial callus tissue and start the process. Having free growth above the cut helps a lot with speeding up the callus formation and it's better to start early in the bonsai development process.
In these examples, I postponed secondary branch structure development for a few years in order to heal large wounds and thicken up the branches primary structure. This free growth period is also a great time to develop a decent nebari.
The Celtis Bungeana featured here, started as an air layer. The diameter of the layer was huge (about 16cm/6.5"). April 2015. It was a low branch that was cut down over and over again for many years because it was growing into a passageway.
It took about 2 months to develop roots and it was cut off the tree before summer.
This is the first repot, at the next spring. luckily there were roots all around the trunk. February 2016.
A year after, continuing the work on the trunk line and nebari. There are a lot of large wounds all over... March 2017.
3 years after, a view of the nebari. Between 2018 and 2020, I didn't repot and it helped a lot with thickening up the roots.
Another look at the tree in 2020. The root flare improved the trunk line tremendously and the free growth completely healed a lot of the wounds.
This is how the tree looks like today (September 2021). I am not satisfied with the branch thickness of the first and second branches. The healing process is pretty much completed and I hope that next year I could move forward to the secondary branch structure. The nebari is also maturing well and I can start planning a bonsai pot for this massive beast.
The next example is of an American Elm and a little different. The surface area of the wound was enormous and although it made huge progress over the last 3 years, I'll need another 1 to 2 seasons before I'll be able to cut back to the primary structure and start to slow things down.
I got this tree in April 2017. I wanted to graft a branch at the low right side and noticed a dead area. After exploration for the live borders, a huge wound was revealed.
This picture is from September 2018. You can see the sheer size of the wound and how fast the tree is healing up.
This Picture is from February 2020. I neglected the tree during 2019 and the healing process was slower. This year I reopened the callus and applied cut paste to speed things up. It is possible to do this procedure at the end of winter and summertime.
The attention paid off. This is how the tree started in 2021. Complete healing could be achieved in a couple of more years and in the meantime, I am not progressing to the secondary branch structure. This enables me to allow free strong growth all year long, allowing faster callus formation.
These pictures were taken these days (September 2021). It will be very satisfying to see a trunk with such a strong taper and movement, with no open wounds visible.
Since bonsai is a long-term endeavor, I think that adding a few years at the starting point, in order to complete these basic tasks in the development process, is important and rewarding.
I hope you enjoyed this post and if you have any comments, thoughts or requests, please feel free to respond.
Shay