Grafting

Grafting is not a subject I would normally advise you to get involved in. The reason for producing a grafted tree is to impart the growth characteristics of the root stock onto the scion. Grafting is used almost exclusively in the production of fruit trees where the producer may wish to make a tree that only grows to a height of say 10ft, but produces a normal crop of fruit, this could be achieved by grafting the scion onto a dwarfing rootstock.

The only time you are likely to encounter a grafted tree in Bonsai is if you buy such a tree for conversion, or with some Pine and Maple varieties that do better on a more vigorous rootstock. For example White pine (Pinus parviflora) is put onto the more robust black pine roots.

The Red leafed cultivars of the Japanese maple (Acer Palmatum), are usually grafted onto normal (green leafed) rootstock, as they don't do well on their own roots. If you are buying a tree from a garden centre to convert into a bonsai, take a good look at the condition of the graft when purchasing the tree.

Look out for bad grafts when purchasing trees from garden centres. A bad graft will often cause the trunk to bulge.

A Grafted apple in an orchard at RHS Wisley. Grownd as a fruit tree the graft is immaterial.

 

Here we have Sa graft on a young, red leaved maple, to overcome the problem i'll layer a new set of roots just below the graft. This will in a short while cause the trunk to swell, hiding the graft and allow the top to continue to grow on its vigourous rootstock.

Grafting has its place in Bonsai if you should need to replace a branch that has died or to put one where it would enhance the shape of the tree, or to put a root where the tree lacks one.

Thread grafting

In the illustration to the right, the tree (a) would benefit from a branch in the area indicated by the red arrow, (b) shows the ideal tree. Tree (c) shows a shoot allowed to extend and (d) the branch in position.

The branch should then be left for a couple of years, to allow the graft to take. When you are sure the graft is ok, remove the unwanted section of the original shoot.

You may then begin to develop the branch.

When choosing a shoot to provide the new branch, pick something long and thin, something you can easily push through a small hole.

Drill a hole through the tree large enough to pass the shoot, with the leaves off. Don't worry if the hole is a bit big, the shoot will soon swell and meet the bark swelling to seal the hole. if you can use a sealant such as Bonsai cut wound paste

Allow the shoot unrestricted growth and when you are sure the graft has taken remove the unwanted part of the shoot and develop the branch

Here we see the tree in 2008. The grafts have taken and the branches are now developing.

Passing the shoot through the tree is, of course is only possible with deciduous trees, conifers will need to have a notch cut in the trunk and the shoot attached firmly, with perhaps a staple, into that notch, then the graft should be wrapped with waterproof tape, stopping the area drying out.

All foliage and buds should be removed in those areas that will end up inside the hole drilled for the shoot to pass through.

Flap Grafting

The foliage of this branch on a cascade pine was too far from the trunk. I decided that by grafting it further back along it's path it would improve the tree. This may take a few years to achieve but will be worth the wait.

A strip of bark was cut back, the branch inserted under the strip and the whole area wrapped (tightly) with plastic tape.

 

Here we see such a graft, this time on a Maple. The wound has healed and when I'm sure the graft has taken, I'll remove the branch coming in from the right and allow the grafted branch to develop.

Grafting roots

If needed you can graft in new roots. The Field Maple shown in the picture to the right lacked a good sized root in the front of the tree. I had a number of fairly well developed young trees, one of which was grafted into the tree to fill the gap.

I had considered layering a new root in, but this, bearing in mind that the trunk was already well developed, would have taken a long time to be effective

At repotting time, both trees were bare rooted and a hole drilled through the recipient tree large enough to pass the smaller tree through (with it's branches removed). The united trees were then repotted and both allowed to grow on.

When I'm sure the graft has taken the part of the 'donor' tree protruding at the back will be removed, but currently it is helping the graft to swell.

Here we see a White pine grafted onto a black pine rootstock. It may take a year or so to be sure the graft has taken. The cut has been bound with raffia to hold it closed. The graft will now be enclosed in a clear plastic bag, keeping the air around it moist.

Most bonsai growers will never need to practice grafting, however an awareness of the technique, may help recover a damaged tree.

Allen. C. Roffey 09:29 24/04/2018