Grafting a kuromatsu

The grafting of conifers such as junipers and pines turns out to be a very useful and important technique, both in order to obtain new vegetation behind in the desired sites, and to improve the vegetation as often happens, for example, on needle junipers (tosho) which are grafted with Juniperus chinensis (mostly Itoigawa). This grafting procedure requires knowledge of some very important techniques and notions in order to guarantee a successful outcome. In the following article I will document the development of a Japanese black pine (kuromatsu “P. thunbergii”) that I have been following since 2013 when I lived in Japan at the nursery of my teacher Nobuichi Urushibata.

The plant had an extremely old trunk, with nice, very natural movement and primary branches all in the right places. However, it required correct grafting, in order to push back the vegetation (long branches), thus continuing its construction in the best possible way. The plants that you decide to graft must always be in excellent health and not be repotted at the same time as the grafts are being carried out, this is to be able to boast of greater strength in vegetative growth which will guarantee a better success rate. Before carrying out the grafts it is a good precaution to carry out one or more fungal treatments on the plant with systemic products. It is also important that all the tools used are sterile and well sharpened (the cuts must not have burrs).

These grafts were carried out in December, but it is possible to graft the pines until mid-February without problems. Obviously after carrying out all the grafts, the plant will have to be protected in a cold greenhouse in harsh climates.

Strong apical shoots were left to grow freely, to be able to use them as scions, having planned the grafting previously. Strong and vigorous shoots with beautiful apical buds should always be used.

Photo above: collect of a scion from the apical area.

Subsequently, the scion must be cleaned of excess needles, cutting them at the base, and leaving 5-7 pairs as a crown. This in order to limit its dehydration until the cambial tissues are welded together.

Photo above: removing excess needles.

The scion must then be wrapped with a special biodegradable cellulose-based tape which prevents it from dehydrating until the graft has welded. This tape is very elastic and to stretch it is preferable to have the help of a second person.

Photo above: wrapping the scion in cellulose tape.

The cut on the rootstock (or branch) must be carried out with extreme precision and must be superficial, in order to have the greatest possible cambial surface available to put in contact with the scion. Be very careful in this operation, both to avoid the risk of damaging the trunk and to avoid getting hurt.

Photo above: making the cut on the branch that will host the scion.

The cutting of the scion is one of the most important elements in order to boast a greater success rate. The cut must be made longer on one side (the one that will go towards the internal side of the cut on the rootstock) and shorter on the other (the one that will go towards the external side of the cut on the rootstock). Furthermore, you should never touch the exposed cambial surface with your fingers because the oils or bacteria present on the skin can damage the cambial tissues.

Photo above: preparation of the scion.

Then the scion, ready to be inserted, must be placed inside the cut previously made on the rootstock. During this operation, use a knife to open the cut of the rootstock until you see that the two elements are bringing the largest possible cambial surface into contact. To conclude, a small quantity of mastic paste is placed outside the graft and everything is tightened again with the appropriate biodegradable cellulose tape.

Photo above: the completed graft.

Photo above: another scion after being inserted into the appropriate site created on the trunk.

Photo above: making another graft.

Photo above: when it is necessary to graft onto a very thick and old branch or trunk, instead of using a knife to make the cut, it is preferable to use a special chisel suitable for the operation. Obviously after having previously eliminated the superficial bark.

About 15-20 grafts were performed on the pine in December 2013.

Photo above: the pine at the end of the grafting procedures.

The cultivation is very important during the following season after being grafted. It must be kept in excellent health and vigor, limiting apical dominance where necessary. Until the grafts begin to grow, breaking the cellulose film, it is necessary to keep the plant in an environment that is not too sunny, especially during spring when temperatures begin to rise.

In November 2015, after a year, it was found that all the grafts were successful, except for one which dried up. We can certainly be satisfied with the work done. In this occasion, the long branches previously maintained were eliminated because they were no longer necessary and another 5 grafts were also made.

Photo above: some details of the successful grafts that growing started to broke the cellulose film surrounding them.

Photo above: the strong grafts are freed from the tape that kept them tight to the branch, as they are now consolidated.

Photo above: the plant after the interventions carried out in November 2015, the unnecessary long branches were removed, the vegetation cleaned and another 5 grafts were made. We begin to see the future structure of the plant.

A year later, in December 2016, the plant presents an even more orderly and delineated shape. This is because the grafts, after two years of free growth, were ready to be wired. Therefore it is possible to give the first real setting to the pine. Even the apical graft, with which the plant was lowered, was now ready to be completely freed.

Photo above: removal of the tape that held the apical graft in safety.

Photo above: the other grafts that were not yet ready the previous year are also completely freed.

Photo above: detail of the wiring of some grafts now that are strong after two years of growth.

Photo above: the pine from the front at the end of the styling carried out in December 2016.

Photo above: the back of the pine.

Photo above: top view of the pine.

Photo above: Before and after for quick comparison.

The grafting of conifers is often put aside because it is considered complex or takes a long time to implement, I hope that this article can encourage as many people as possible to try their hand at this technique to surprise themselves with how rapid the construction with the grafting is in terms of bonsai years. Anyone who has any doubts or would like clarification, please do not hesitate to contact me.
Greetings you all!