Bonsai Basics - The Trunk
Alan RochesterThis article is being reprinted from our October 2002 magazine and was written by Alan Rochester. Alan was a founding member of the club and very influential through his nursery.
A good trunk can make the visual difference between an aged tree and a juvenile tree. After you have established the root system this is the next stage you need to work on. The trunk should have the look of an aged tree and must have taper from the base right up to the tip or apex of the tree. The size or diameter at the base should be of good size compared to the height of the tree but is not always the case.
A tree that has a large diameter base is usually a tall tree, but a stunning effect can be achieved with a short stocky tree that has a large base but is short in height. This style is particularly used with Trident Maples and Figs. Note, it is extremely important with this style that the tree has a perfect taper right to the tip and not looking like a stump with a chopped top.
Tall trees with a slender trunk can look good also, particularly if designed in the Literati style and the sinuous upright style. Azaleas are often styled in the Sinuous style whereas Liquidamber, Hawthorns, Maples and Red Pines can look good with tall slender trunks.
Pines are a good species to design in the Literati style. Normally small diameter trunks are small in height.
To get a good size trunk you may have to grow the tree in a large pot or in the ground for a couple of years. As the tree grows in height you will need to prune it heavily back down to a new leader and let it grow up again. This process is continued for a number of years, depending on how thick you desire the trunk to become and a nice taper has been developed.
The branch system is not important at this stage though if you have a picture in mind of your tree you may start to develop a minor frame at this time, remembering that you may slow the process down if you concentrate on developing branches at this stage. Fertilise the tree well and give it plenty of water as this will speed up the process of thickening dramatically.
A problem that arises with this method of speed growing is that the tree can lack character, because of the speed of growth. Everything usually grows straight and stiff so you will need to wire the tree or use ‘clip and grow’ method. This is where you prune to a bud in the direction you require the tree to grow. Chinese Elms, English Elms and Crepe Myrtles grow well with this method.
If you do use wire you must keep a very watchful eye on it because it will cut into the trunk and bark extremely quickly. Scarring can occur with speed growing because of the number of times you prune and make large cuts. Some people think scarring is ugly but if the cut is done properly the cut can heal without much damage at all. Also features can be made from large scars in trunks by developing a hollow trunk style (sabamiki).
When developing a trunk the best materials to start with are ideally young trees i.e. starters up to 5” pot size. Using young stock allows you to control the shape and style of the tree from the start and therefore you’re not dictated to a style with an older, more developed tree. Wiring a young trunk is much simpler and gives you more freedom in choice of styles.
When cutting down larger stock you are normally limited to only a couple of styles, if that! Trees that are developed from when they are young will develop with fewer faults and scars.
The trunk should have movement in it to create interest unless you are looking to develop a Formal Upright style. The trunk should move left or right and slightly forward. After the trunk has been trained the next stage may begin - The Branch Structure.
