Bonsai Containers, Soil, Potting and Repotting
The choice of container will be very largely a matter of personal taste. There are, however, a few points which must be taken into consideration when trying to select the most suitable container, and we should not lose sight of the meaning of the word bonsai; ‘bon’ means shallow pan, and so it is important to keep the pot as shallow as possible; too deep a container will look specially ugly when planted with a small bonsai.
The top surface area of the soil should be kept in proportion to the size of the plant. For single upright specimens a round or oval container is suitable; but where more than on tree is grown in a container, or when the oblique or cascade style is chosen, a rectangular shape is usually more artistic and pleasing to look at. The size and shape of containers chosen are dependent on the question of proportion, and the grower should let this be his guide. Some pot making firms still produce oval, square and oblong seed and alpine pans an d these can also be found sometimes second-hand in sales.
Glazing is matter of great importance. In almost all cases bonsai will thrive best and longest in completely unglazed containers. In Japan there are potteries that design and make bonsai containers and these are always unglazed inside. With growing interest in bonsai, it may well happen that more potteries here will again make unglazed containers specially for bonsai; they are also most suitable for bulbs.
It is most important to have drainage hole in each container. A small pot will only need one hole, but a larger one may well need more. Holes can be made by very carefully drilling with a hand drill and his will often be necessary if containers are brought in antique or bric-a-bric shops. It is always worth looking in these places for suitable containers as often a ‘pot’ may be found to suit a particular specimen.
The color of the container can do much to enhance the appearance of the specimen, but it should always be as natural as possible -- i.e. shades of black, brown and green; in a few cases white can be most effective. On the whole evergreen specimens look their best when not seen in a green container. When a container is to be chosen for flowering bonsai, the color of the flowers must naturally be considered. For example, if a pink or red Chaenomeles is to be potted, containers or common earthenware flower pot color need to be avoided, and forsythia would not look well in a container of yellowish shade.
These can so much more easily detract from the appearance of the bonsai than add to it, that they should be avoided. The Japanese seldom use them and when they do the ornaments selected are very small and usually of antique origin.
Most bonsai will remain in same pots undisturbed for a year; some two or three years. During this time they will be watered and fed frequently. For this reason it is important that the compost used should be of such a form that it does not become waterlogged or sour. Always use a good safe standard compost; and if you feel that you would like to make up one of your own, the following proportions give a good mixture:
- 2 parts good, fresh fibrous loam
- 2 parts coarse sand
- 1 part leaf mould
The soil eventually used should not pack down too hard in the pan as this excludes air which is vital for the healthy growth of the tree.
As a general rule guide it is safe to say that bonsai are best potted or repotted while they are dormant -- just before the growth starts in the spring.
Before potting up a seedling or repotting an older specimen, water it thoroughly an hour or so beforehand. The compost to be used should be moist enough to bind when squeezed in the hand, but not so wet that it will not crumble again easily between fingers. The drainage holes should be covered with broken clay pots (curved side uppermost) or zinc gauze disks, and these in turn covered with root fiber to prevent the soil washing into the drainage holes.
The container may be considered in the same light as a picture frame and having discussed the shape and color of this ‘frame’, we can now look at the position of the subject in it. The perfectly shaped upright bonsai is best planted in the center and when one is potting all bonsai, care should be taken to see that the best side of the tree is kept to the front. Bonsai of the cascading style need planting to one side -- that over which they cascade. If a tree is more heavily branched on one side, it is best planted off center so that the heavier side is over the largest proportion of the soil.
As far as group planting is concerned, the highest plant should be about one third of the way in from the edge of the container.
When potting, make the compost fall evenly among the roots by sharply tapping the ‘pot’ on the bench and then firming with the fingers, leaving about a third of an inch space for watering; in some cases a small pointed (not too sharp) stick will help get the soil into all the crevices; the Japanese use chopsticks.
If suitable attractive chippings or pebbles can be found to spread on the soil surface, these will often help to prevent it becoming hard or ‘panned’ with frequent watering. sometimes a few very carefully selected pebbles or miniature rocks to one side or end of container look more attractive, though of course these do not fulfill quite the same function.
After potting, water thoroughly and keep evenly moist thereafter. If the plant is an evergreen, or a deciduous plant with leaves, keep it shaded from hot sun until it is well established. In very hot and dry spells frequent syringing with a fine mist will be very beneficial.
The soil, method of potting and after care are same for repotting as for potting, but one or two things need to be considered.
Repotting bonsai does not necessarily mean transferring to a larger container, as this may promote too much growth. For bonsai which are not in the very early stages of training the same container may be used with partly new soil. If the specimen is in need of rejuvenating, it is advisable to remove all old soil from the roots and replace it with fresh compost. Fast growing plants, including most deciduous trees and shrubs, need repotting every year; slower growing plants, including most conifers, may need repotting only every two or three years. Bonsai that are pot bound, or those that give indications that the soil is sour or too hard packed and airless, must be repotted as soon as these points are noticed, but the best time to do this work is undoubtedly just before the season’s growth starts.
When repotting is to be done, the plant should be watered a few hours beforehand so that the soil has drained before the removal of the container. This is done by holding the stem between the fingers of the left hand and then turning the container upside down and giving it a sharp tap on the potting bench or table.
First of all remove all old drainage material and then about one third of the old soil, mostly from the bottom, but also a little of the original surface soil. It may be necessary to use a pointed stick, similar to a chopstick, to remove the soil from between some of the roots. Any long roots exposed should next be trimmed with a sharp knife or secateurs, to leave about a one inch space between them and side of the container, which will be filled with the fresh compost.
The actual method of repotting is as for potting and similar drainage must be provided. It is most important to report the specimen at the same depth as before. After repotting, water the plant and keep it in a cool shady place, taking care not to overwater it as the roots will not be very active until they have re-established themselves; syringing in hot weather will help the plant to recover from the disturbance. Any necessary pruning or wiring is best postponed until the following year so that the plant suffers no further setbacks, unless it starts into very rigorous growth during the summer.