Bonsai is an old Chinese art of growing trees. Bonsai comprises a tree or shrub planted in a small container for developing as a miniature plant showing the general appearance of that plant species found in nature. It differs from a pot plant where the foliage and flowers are important whereas for Bonsai the appearance of the plant in a miniature form is to be maintained for many years.
Plants Suitable for Bonsai
Although the suitability of plants for developing as Bonsai has been tested in Japan consisting mostly of sub-tropical and temperate plants, very little information is available on the response to the growth of tropical trees in miniature form. Late Shri V.P.Agnigotri has developed a technique of dwarfing trees commonly found in this country. The suitability of a tree to develop as a Bonsai depends on various factors:
Among the tropical trees that thrive well as miniature plants are: Adonsonta digitata, Anthocephalus cadomba, Bombax malabaricu, Adenanthera pavonina, Brassia actinophylla, Butea frondosa, Caesalpinia coriaria, Erythrina cristagalli, E.parcelli, Ficus religiosa, F.bengalensis, Jacaranda mimosaefolia, Kigelia pinnata, Putranjiva roxburghii, Tabebuia chrysantha and Thespesia populnea.
Several tall shrubs like Adenium obesum, Brya ebenus, Fortunella japonica, Hamelia patens, Hibiscus schizopetalous, Jatropha podagrica and Murraya exotica form very attractive dwarf plants. Woody climbers like Combretum, Derris scandens, Hiptage madhablata, Roupellia grata and Jasminum auriculatum can also be trained as Bonsai. Among the conifers grown in tropical conditions, Juniperous prostrata and Pinus khasiana will form good Bonsai.
Growing the Bonsai
Plants suitable for growing as Bonsai are planted in small containers. In tropical climate, the monsoon is the best season for planting or transplanting. For making Bonsai, plants growing wild or seedlings grown in the nursery for several years should be carefully uprooted, grown in ordinary pots for a year or two and then planted in a shallow container. Plants may also be obtained from layering of a large branch, grafting or by raising seedlings in a pot.
It is advisable to grow the plant in the ground for a year or two which helps in developing a strong root system and healthy branches. They are the transferred into a container after pruning the roots and branches. The plants grown in pots may also planted directly in the container.
The containers should be unglazed shallow pots of various sizes and shapes. They may be round, rectangular or square, the size and depth depending on the plant to be grown. The containers should be simple and non eye catching.
The soil for potting should be fresh, well-drained, and on very rich in fertilizer. It should not be highly acidic or alkaline. Clayloam or loam of different structures and clump sizes, obtained by sieving the soil is used in potting. It should not be very sticky or sandy. Well-rotted leaf mould is mixed with the soil.
The soil is dried in the sun and sieved through meshes of at least three sizes. Large, medium and fine soil obtained by sieving are kept in separate containers. At the time of planting, the larger particles are placed at the bottom of the pot and a thin layer of medium-sized particles is spread over it. The tree is planted and the top soil consisting of small particles holds the plant in position and comes in close contact with roots.
Removal of tree
The soil of the plant to be transplanted should be kept on the dryside to facilitate removal of the plant from the pot. It may be necessary to remove thick roots and also the tips of some fibrous roots with a pair of sharp shears. After pruning the roots, the shoots are pruned depending on the growth habit and the desired appearance of the plant in miniature form, when the branches are crowded in any part of the plants. In the case of unbranched seedlings growing terminally, the main stem is cut to a height, which may form a well-shaped Bonsai.
If the branches are small and well arranged, pruning is not needed but the terminal growth is removed to minimise the height of the plant and to encourage the growth of auxillary branches. In case the branches have already grown to a size too tall for a Bonsai, they are pruned to 1/2 to 1/3 the length depending on the rate of growth of the plant and its response to pruning. Generally broadleaved plants and harder pruning than small-leaved conifers.
Planting in Container
The holes of the container are first covered with crocks or plastic net. Then a layer of large soil particles is placed with a thin layer of medium-sized soil above it. The tree is then placed in the soil. Before it is finally planted, the side presenting the best view should have been determined. The medium-sized soil is placed around the root region a consolidated by means of a bamboo stick without pressing too hard. Then a layer of fine soil is spread on the top, levelled and pressed gently. While planting, care should be taken to keep the base of the trunk from where the main roots rise above the soil and to place the plant in the middle of the container. After planting, watering should be done with the help of a fine rose from the top of the plant.
Care of the Plant
The container is kept on a platform in a cool and shady place for about two weeks to allow the roots to develop and the plant to establish. It is then gradually exposed to sunlight for longer durations beginning with the morning sun for two hours. The soil should never be allowed to dry up completely. In summer months with high temperature and low humidity, the plants may be placed in shade in the midday and afternoon. They also need protection from frost. The miniature plants should be arranged in a planned fashion on a plantform or on stands of different sizes and heights so that the collection of plants looks like a garden. Proper spacing between the rows will facilitate watering the maintenance of the plants.
Watering is very important for Bonsai, as they are grown in shallow containers with small amount of soil. They should not be allowed to dry as temporary wilting of the plants adversely affects their growth. If the roots shrivel due to shortage of moisture in the soil, the plants are likely to die. Excessive watering often causes poor growth and waterlogging for a considerable period may cause rotting of the roots.
Pruning and Pinching
Removal of buds from Bonsai is an important practice. Pruning maintains the shape of the plant, stimulates branching and helps in the utilization of energy for the growth of other parts of the plant. The frequency and mode of pruning will depend on the growth habit rate of shoot growth, response to pinching and subsequent growth of auxiliary shoots.
In order that the plant may maintain an attractive appearance, pinching is not done at the same length in all the direction. In the case of two axillary branches growing in two directions, one may be pinched at the apical bud, while the other one is pruned up to several nodes below the terminal bud. If the plant tends to grow fast in a particular season or continues to grow in length throughout the year if may be necessary to pinch more than once a year. But frequent pruning leads to the formation of thin and weak shoots, which may wither in an unfavourable environment. Pinching or pruning should be done clean without damaging the shoot at the cut end It should be ensured that the plants remain in a fixed position and the soil and root are not disturbed at the time of pruning. Bonsai varies in shape and size. Following are common types:
Arrangement of Branches
The arrangement of trunk and branches is also an important technique to be followed to develop an attractive Bonsai. It is done to improve the shape and to help in the manifestation of natural appearance of the plants. In order to maintain the space between two branches the lower one is suspended by a strong twine or wine.
Before using wire, the portion of the branch is wrapped with raffia where the wire is to be tied. To improve the arrangement of the branches on the plant, wire is to be used very carefully and the technique needs experience, skill and proper tools. Wire cutter and pincers are normally used for the purpose. Copper wire is better than iron wire, as it is softer and can be seen easily and does not rust.
Another very effective method of modifying the shape of the tree or arranging the branches is to tie wire around the trunk or branches so that they may grow in the desired direction and form.
Bonsai needs repotting when the soil is completely exhausted or the container is filled with roots. In general, plants in the growing stage are repotted once a year, and a full-grown tree once every two or three years. Containers should be used after thorough washing and drying. While repotting, the old soil should be removed as far as possible and dead roots and ends of fine roots pruned. Unnecessary branches are also removed to improve the appearance of the tree. Then the Bonsai is planted firmly in the container using the similar type of soil mentioned earlier.
Application of Manure and Fertilizer
Fertilizer is necessary for Bonsai as the plant thrives and grows in a small container. One kilogram of mustard cake is diluted with six litres of water and allowed to decompose thoroughly. After about 3-4 weeks, the water above the decomposed manure is again diluted with 5-10 times the amount of water and the dilute solution is applied to the soil leaving the base of the trunk. Thoroughly powdered cake is lightly mixed with the topsoil slightly away from the trunk, in two or three areas using 1-2 tablespoonful of cake in each case.
The plants should be manured in the spring and again in the rainy season when they show vegetative growth. During the growing season the plants can be manured once a month followed by watering.
Control of Diseases and Pests
Diseases and pests are common with Bonsai. Root rot is a common and serious disease caused by excess watering, drying of soil, poor drainage, direct contact with undecomposed organic matter, etc. the affected plant will show poor growth and decay of shoots. In the case of fungus infection either on shoots or on root, the diseased part should be removed at the earliest opportunity. Spraying of insecticides and fungicides should be a routine practice.