However low the price of ready-made bonsai may fall to satisfy the market, nothing can rival the satisfaction of growing your own. Whether you start with a seedling or an ancient tree rescued from a lost garden, the intimacy of working with nature to create a thing of great beauty has a profound effect on the soul. Enjoy it to the full.
An expert practitioner conducting a workshop for an enthusiastic group dedicated to the practice of a venerable and ancient art.
Exhibits at the famous Kokufu Ten bonsai exhibition which attracts well over 20,000 visitors to Tokyo each February.
BONSAI
Science or art?
It is sometimes asked, whether bonsai is simply a horticultural discipline that requires an understanding of how trees function and how they respond to external factors, or whether it is an artistic challenge to use an ever-changing medium to create an object of beauty. Ideally, it combines the two: it satisfies the basic human need to commune with nature and the creative urge that lies within us all.
CROSS-SECTION THROUGH A SIDE ROOT
THE FINEST SINGLE-CELL ROOT HAIRS ABSORB WATER AND NUTRIENTS FROM THE SOIL AND DISTRIBUTE THEM THROUGHOUT THE TREE.
Anatomy of a bonsai
The roots
We take it for granted that all plants have roots of one kind or another, but if we’re going to be responsible for keeping a tree alive and in the best of health, it is essential that we understand a little more about them.
The function of roots: Roots have three primary functions. The first is, quite simply, to stop a tree from falling over. The roots that spread out from the base of the trunk extend in all directions, anchoring the tree in the soil. This applies equally to bonsai. If a bonsai is easily rocked in its pot, then the roots are failing and, if the roots are weak, the tree will also be weak.
A thick taproot and a mesh of finer side roots on a young plant. The taproot is the first root to develop on a seedling; it provides anchorage and seeks moisture.
The second function of roots is to draw nutrients and water from the soil. Species that are adapted to grow in arid regions have long, searching roots which tap moisture from a wide area.
Others that live in moist, fertile soil have fine, shallow roots that may not extend beyond the spread of branches. A tree living in the confines of a bonsai pot must have a well-developed, efficient root system to stay healthy.
The third function of the roots is to act as a pantry for the tree. During the dormant season the roots store sugars that were manufactured by the leaves throughout the summer months. The storage areas are in the heavy, woody roots, so it is vital to develop and preserve an adequate number of these sturdy roots on your bonsai.
How roots work: If you examine the roots of a tree or shrub, even on a small nursery plant, you’ll notice that there is no taproot. The taproot is the first root produced by a seedling; it grows directly downward to seek out moisture while it provides stability. People used to think that the taproot continued to extend downward for a considerable distance, but that is now known not to be the case.
Roots will only grow down as deeply as they need to locate a constant supply of water; and, in most cases, that is not very deep.
It is worth noting that the roots are structured rather like the branches; the thickest roots radiate outwards from the base of the trunk, they then fork regularly and terminate in masses of fine roots at the tips. In a full-sized tree, these fine feeding roots may be located way beyond the outer reaches of the branches and cover a massive area.
In a bonsai tree, however, the roots don’t have the luxury of wide open spaces. They must be super-efficient and able to gather all that the tree requires to keep it in good health from a relatively small volume of soil. To do this effectively, the majority of the roots should be encouraged to become very fine and dense in close proximity to the trunk.
Moisture is drawn into the plant for absorption by osmosis, first and foremost via the finest of fine root hairs. These single-cell outgrowths occur all along the length of the growing tips of the fine roots. In some cases they are so minute as to be impossible to see without the use of a magnifying glass, while in others they are large and long enough to be noticeable. The process of osmosis is a simple one and is worth investigation at this point.
A sturdy set of aerial roots on a Banyan Fig (Ficus retusa), which makes for a particularly effective bonsai in the Root-over-Rock Style.
Osmosis – a fair exchange
The walls of the root hairs are permeable, that is to say, water molecules are able to pass through them. The fluid inside the cells of the root hairs is packed with a high concentration of nutrients in the form of mineral salts, while the water on the outside contains a much lower concentration. In order to balance the two, water passes from the moist soil through the cell walls and into the root hairs, in effect, causing the dilution of the concentration contained within the root. As the water passes through the cell wall it carries along with it the nutrients it is holding in solution.
If the concentration of nutrients in the soil is higher than that within the roots e.g. if you have given your tree more than the recommended dose of fertilizer, water will pass from the roots back into the soil and the roots will die of dehydration. This is what gardeners call ‘root burn’, and it explains why smart gardeners allow farmyard manure to stand and rot for about a year, before applying it to the soil.
The thicker roots act as winter storage vessels for sugars that the leaves have produced during the summer months. The sugars are passed down to the roots for storage in late summer and remain there until the buds begin to swell in the following spring. At this point, the fine roots begin to take on water to pump into the swelling buds. As the water is passed upwards through the roots and into the trunk, it facilitates the growth of new shoots and leaves. Once they are properly established, the new leaves are able to support themselves fully and the same cycle begins all over again.
These nebari, or thick roots, anchor the tree in the soil and act as pantries for the plants by storing sugars over the winter months.
Healthy roots mean healthy trees
The experienced bonsai grower knows that if a tree looks seedy, it is likely to have something to do with the roots. It might be that they are growing in an environment that is either too wet or too dry; they may have been damaged by frost or by insect larvae. Also, the roots may have been overfed; or perhaps they are not able to gather enough nutrients or minerals from poor soil. All these points will be covered in greater