Bonsai is an art form from East Asia that employs cultivation techniques to create small trees in containers that resemble the shape and scale of full-grown trees. Specific attention is usually required on the trunk of a bonsai simply because it is one of the most attractive features of any tree. Some of the cultivation techniques used by growers lead to problems that result in a weak or narrow trunk. However, some methods can be used to thicken and strengthen a Bonsai trunk.
Best working techniques for thickening a Bonsai Trunk
The following are some of the techniques that can be used to thicken Bonsai trunks. You should note that some of them may take much time to get the desired results.
Splitting the Trunk
This is the quickest method to thicken your bonsai trunk. You need to split it down physically in the middle and use a wire to keep the two halves separate while the trunk heals. When employing this technique, you must remove the bonsai from the pot and remove all the soil in its roots. Split the trunk in the middle using a saw while holding the tree in an upside-down position. After that, you can return the tree to its pot with the help of wires or wooden edges to keep the two parts of the trunk from each other. This technique should be used on species that can cope with this type of injuries, such as elms and boxwood.
Induced Trunk Swelling
This is an old method used by the Japanese. You should place a wire tourniquet on the base of the tree to induce swelling. This technique will give you quick results in a single growing season when you apply to a fast-growing material. The scar left by the wire tourniquet will still be visible but its effect on the trunk will be visible as well. The technique results in the thickening of the area around the base only. Therefore, you should make a tapered trunk in species that do not taper naturally, such as the Chinese elm. Take care when using this technique, as it leaves a permanent scar behind.
This technique is mainly used to thicken the trunks of a pine or Juniper tree. With the help of a knife, you can carve vertical lines on the back down to the sap layer. The carving will result in an injury that the tree will recover from. Scar tissue will be produced that will lead to the thickening of the trunk. The Juniper Bonsai is one species that has shown good results when a reverse taper was done mid-trunk. Its trunk was cured in this way, since it only requires single scarring. The technique is repeated once every two years to heal the reverse taper. A trunk can be thickened at the base when you carve three or four scars around its circumference and leave it for some time to heal.
Growing in Large Trunks
This method will give you formal and upright trunks with a good taper. You need to plant the tree in-ground or use an escape technique whereby you plant them in a larger can. This will give allowance to the roots to escape through the drain holes of your nursery can down into the earth’s surface. You should also remember to continue watering them through the can. When the time comes for harvesting the tree, you will simply cut its roots at the can. These roots will still have an intact root ball. The top of the tree must be given time to recover before you can cut its trunk. When using this technique, you should let the tree grow naturally to a point where the top can wave in the wind. This will result in the development of large buttressed trunks after a period of close to 5 years. Thereafter, you can break the tops and Jin in the upper part.
Some other techniques can be used to thicken a bonsai trunk. However, some of them can prove to be very risky and dangerous and will require extra caution. The above techniques have been used for a long time and their results are guaranteed. Therefore, you should choose the technique that is easiest for you.