Prior to last week I had only tried sandblasting on one small cedar. The results were excellent, but I was limited to using my friend’s small parts sandblasting cabinet which could only handle a shohin sized tree. Recently, however, a member of our club got a full sized sandblasting tank and offered to let me try it out on some larger trees. Often sandblasting is done in an enclosed tent or room, but we just did it out on his lawn.
This tree was collected in spring 2013. Last year I did a rough initial cleaning on it using hand tools, but with a craggy old thing like this, sandblasting is the most efficient way to clean away all the old dead bark while preserving the details of the deadwood. Many of the cracks and crevices are impossible to access with hand tools. Sandblasting should be a once-in-a-lifetime event for a tree. Once it is done, the deadwood can be maintained over the years with gentle brushing (water and toothbrush) and lime sulfur application (although this is often unnecessary on thuja as their deadwood will naturally bleach in the sun as long as it is clean).
We used aluminum oxide media at 50-90 psi.
The tree before sandblasting. The trunk was wet at this point as it had been raining, so it is much darker looking than it actually is.
Preparation is important. Covering the soil prevents it from getting blown away. Covering the foliage is absolutely necessary – it will die if it is hit by the media. We chose to cover the live vein with modelling clay as insurance, although this is not strictly necessary if you are careful -the bark is surprisingly resistant to sandblasting. I’ve seen pictures from Takeo Kawabe’s book (Kimura’s student) who seems to sandblast junipers with no live vein protection.
After about two hours of sandblasting. 90% of that time was spent drinking beer and waiting for the tank to re-pressurize. Sandblasting requires a high CFM compressor and the one we were using was unable to keep up for more than a minute or two.
The medium we used left a slight texture behind on the deadwood but it is all we had to work with. I am still very happy with the results. The live veins will be further defined over the coming years.
This heavy break will unfortunately be hidden in the back of the tree. It is gorgeous but there are always compromises with yamadori.
Another candidate for sandblasting. This tree was probably collected in the 80s and was once a bonsai, but had been growing as a garden shrub for 10-15 years. Most of the branches are unusable and it will be a challenge to bring this one back. I’ve been rehabilitating it for two years, but you can only expect so much backbudding from a thuja.
After blasting. No trunk protection was used to sandblast this one.
You can see where some of the bark was blasted away, but nothing too major. I will likely polish the bark on this one anyway.
Original front of the tree 20 or so years ago. It is likely to become the new back as the deadwood is quite flat and the inverse taper more pronounced.
An old picture of the tree from the Toronto Bonsai Society website.
This tree was also sandblasted then a basic structure was set. Sorry, no before picture. It was collected in the 90s by a senior club member and is also quite overgrown, but not as bad as the previous one. It could be presentable in two years.
It is looking very sparse right now due to the removal of old foliage and unnecessary branches, but hopefully it will fill in before the end of this growing season. Its current sparseness gives an opportunity to see the strange relationship between the two trunks. As the foliage fills in, the pads and the spaces between them will become more well defined.
This tree is big, about 65 cm tall from the lip of the pot, and weighs about 75 lbs. The two top jins are of equal height – a problem which I will address the next time I work on the tree.
This is a photoshop adjusted picture showing how I would like to reduce the top jin on the right, and bend the jin on the left so that it better matches the overall movement of the tree.
Right side. I’ve always struggled with the flatness of the main trunk, but yamadori always have their faults.
Most of the old crusty larches I collect need grafting. It seems the older they are, the farther the living foliage is from the interesting part of the trunk. Three thread grafts were started on this larch in spring 2014 and all three of them failed this summer (despite not yet being separated from the donor branch).
Three dead grafts. The middle one was the most important as that was to become the new leader of the tree. The one above that… well it was too high i.e. a mistake.
I’m not sure why they failed, but I think it might have had something to do with long period of time elapsed. Ideally, once started, a thread graft will grow rapidly and then take within a few months. Unfortunately, these grafts hardly elongated last year therefore they had no change of reaching the thickness required for fusion until they really started to take off this year. But in July of this year when they should have been fusing, they were instead girdled and died. This is purely anecdotal, but I believe that the callus that formed around the edges of the drilled hole was somehow too hardened-off or otherwise too old to readily form a graft union with the threaded branches by the time they were thick enough to do so. Or maybe the drilled hole didn’t form a callus at all.
Anyway, they failed and I needed to re-graft. Late summer is not a good time for thread grafting larch, so I tried a traditional approach graft instead.
I’m not sure what these nails are really designed for, but in Japan they are commonly used for grafting. With this graft they are not going through the branch, but are just adjacent to it. With thicker branches it is OK to hammer them right through the branch. They do an outstanding job of creating a very snug graft junction.