How to Make Bonsai Trees: Grafting
This method of propagation is based on joining the living tissue of two growing plants, which may be different, yet closely related, compatible species. The method allies the aerial part, or scion, to the stock growing in the ground. The plant produced will have the characteristics of the scion.
Grafting is of interest for creating bonsai, since it guarantees the transmission of very specific characteristics, which is not certain from seeds. Above all it is a way of obtaining a particular shape and style quickly. Some plants can only be obtained in this way, such as certain fruit trees from stones or pips, which make most attractive bonsai.
DIFFERENT GRAFTING METHODS
A great many grafting methods are used to unite various plants, most of them requiring little but highly specialized equipment: a double bladed grafting knife with one straight and one curved blade, raffia (for grafts which need tying) and special mastic for grafts which do not need tying.
The various methods described will unite one plant to another efficiently, but remember that grafting often leaves a visible scar, which can spoil the appearance of a bonsai.
This is the ‘gentlest’ method, since the scion is not removed from its parent until the graft has taken. The technique is simple: remove a piece of bark from both scion and stock with a grafting knife (taking care not to damage the wood). Then press the two against each other so the cambium layers are in contact and tie with raffia. Do not use mastic. If the rings of growing tissue coincide perfectly, the two plants will quickly fuse. Bring the two plants together when their growth is most active, preferably in early spring. When the graft has taken, the plants can be separated, but not before the end of the following winter. Then cut the stock above the join, and cut the scion just below the join. The binding can now be removed. To help heal the scar and to make it less unsightly, cover the wounds with mastic.
Here, the parent stock is cut through horizontally. The cut should be made with sharp secateurs or a saw and should be perfectly clean. Trim the cut with the curved blade of a grafting knife, which should also be used to make a vertical slit in the centre of the parent stock. Trim the base of the scion with the curved knife blade until its wedge shape slides easily into the slit. Then tie the graft and, lastly, seal it with mastic.
Like cleft grafting, this needs a good, clean cut, but the slits should not be made right across the stem. Vertical slits should be made in the bark in three places, 3-4 cm (1-¼ – 1-½ in) apart. Cut the ends of the scions to a taper, then insert in the slits. A grafting knife is essential for making the slits and lightly peeling back the bark, as well as for trimming the scion. Use the small spatula at the other end of the knife to peel back the bark. When the scions are in place, bind the graft and apply mastic. This type of graft will be of special interest to those wishing to produce ‘broom’ or ‘weeping’ style bonsai.
Simple to carry out, side grafting entails making a slanting cut in the side of the stock into which the wedge-shaped end of the trimmed scion is inserted. The graft should then be bound and sealed with mastic.
This method is especially good for grafting conifers and evergreen trees. The cambium layers of scion and parent stock come into contact and this helps the graft to take.
This technique is very different from the others described, since it does not involve grafting a twig, but an eye or leaf bud attached to a small piece of bark. The bud is inserted into a T-shaped cut made in the bark. As with crown grafting take care not to damage the wood when doing this and use the knife’s spatula end to open the bark a little. Insert the bud and then bind, but do not seal with mastic.
This method of grafting is probably gentler than the others for the stock, which is not damaged if the graft does not take. It can be carried out in summer when bud development is well advanced.
THE ADVANTAGES OF GRAFTING
As we have seen, grafting can be considered one of the most reliable methods of propagation. It also makes for a considerable saving in time, compared with raising from seed.
Grafting also offers the bonsai enthusiast other benefits, such as improving the shape of a tree. It is possible to use the bonsai tree’s own branches to add a branch where one is missing. This takes grafting out of the realm of propagation and into that of bonsai shaping.
Grafting is also used to alter the gender of trees, making a sterile dioecious tree monoecious and fruit-bearing. It is enough just to graft a branch from a male tree on to a female one to provide for notably easier fertilization of the.
Contrary to popular belief, grafting mastic plays no active part in the ‘taking’ of a graft. This is proved by the fact that a number of grafts do not require sealing, the contact between cambium cells which ensure a union, being enough just with binding. The addition of mastic is only needed where a large proportion of tissue has been exposed and needs protecting from airborne diseases.