So, I had intended to follow Harry Harrington’s suggestions as regarding re-potting Oaks, but as is sometimes the way, things don’t always go to plan! In this case mother nature had other ideas.
After a very mild winter we had got to late March/early April and Mr Oak already had buds swelling. The Oak saplings I had bought the previous autumn were also showing strong signs of growth. There was no way the next process I had planned was going to wait until leaves had emerged as I had originally intended. So I waited until the buds were really fat and almost opening and then got cracking with the repot and root grafts.
The first thing I did was to get the pot ready for it’s new occupant. Tie down wires and mesh covering the drainage holes all attended to I got to work with removing the tree from it’s old home. (Fig.1)
It had been in it’s old pot for at least 5 years, but probably longer as John Hanby acquired it from the previous owner in 2015 and John hadn’t re-potted it. To say it was a bit pot bound was an under statement! (Fig.2) I started to work on the old root ball and it took me around an hour or so to get all the roots untangled. I washed the roots with the hosepipe and got rid of all the old soil. I then pruned off the really long roots that had been circling the old pot. They would be of no use in it’s new home.
The next process was getting to grips with creating the thread grafts. Following the instructions that Danny Use had written in an article from an old bonsai magazine I started work. First I needed to place the main tree in it’s new pot so I knew excactly how much room I would have to fit the thread graft roots in. I used a couple of wooden wedges to achieve this. I also kept a small spray bottle of water beside my workbench to occasionally spray the roots to prevent them from drying out.
I removed the compost from the first sapling and having worked out where I wanted the extra roots around the trunk I offered it up to get the correct length. After doing this I cut off the top of the graft tree using a pair of concave cutters to get a nice clean cut. (Fig.4) I matched a drill bit to the diameter of the top section of the graft material and drilled the hole in the main trunk where I wanted it. The recommended depth to drill to is 1.5cm. (Fig.5) This was done and then the bark was removed from the top 1.5cms of the graft material. The graft is then inserted in the hole ensuring the edge where the bark was removed is in line with the bark on the main trunk. The graft is secured in the main root ball and cut paste is pushed around the joint.
I then performed the same task on the other two saplings and the root grafts were complete. Three in total, as it turned out to have a better root spread than I had first thought it may have. (Figs.6 & 7)
I removed the whole tree and it’s new additions from the pot and set too potting it up. I placed a mound of my own deciduous bonsai soil mix just off centre in the pot followed by a good sprinkling of chopped sphagnum moss. (Fig.8) I have found this to be an excellent addition to newly potted trees that have had major root work done on them as it really helps with recovery. I then placed the tree at the angle I wanted and twisted it back and forth on the mound to make sure that soil was driven into the underside of the root ball. Taking care of course not to dislodge the new grafts. After this was done I got my jin pliers and twisted the tie in wires good and tight across the roots to support the tree until it had gotten established in it’s new home. I resumed adding more substrate to the pot a little at a time and working it in and around the root ball to ensure there were no air pockets left and that all the roots were (theoretically) surrounded by substrate. (Fig.10)
It got a good drenching and I kept the water trickling through until it ran clear. This is to ensure no fines or dust remain in the small spaces within the substrate. It was then placed into the greenhouse for 4 weeks to recover. After which it will then go into my shade house for a further 2 weeks before it resumes it’s place on the bench back in the main garden.
I will leave it to grow freely this year, fertilising it after the leaves have hardened, to allow it to regain full strength and vigour. Then come the autumn after leaf fall I shall do some selective pruning of the branches to bring the overall image back…..
I shall post a few pictures as the year goes by to show progression.