General careContrary to a popular misconception, the first principle of bonsai culture is to maintain the trees in a healthy state. The dwarfing of a tree is not achieved by soil starvation or by having the tree the minimum water necessary. Nor is it necessary to perform strange rites before a bonsai tree. Bonsai trees have similar needs to the oak or the tiny daisy. The essence of their care is continuity and regularity; a few minutes a day is infinitely better than a couple of hours every two weeks.
Fertiliser and humus
Adding humus to the tree should not be necessary as this vital element in the soil is added then the tree is repotted.
Fertiliser should be given at regular intervals from Spring to Autumn. Inorganic fertilisers are not often used with bonsai trees as their action is too sudden. Organic fertilisers have a low
continuous action. However, if a tree needs a quick lift then inorganic is preferable.
One of the easiest methods of fertilising is to use an organic liquid feed that can be bought from
a Garden Centre or a garden shop; it might be added that it is not essential to use Japanese
fertiliser such as soya bean mash, rice bran etc. Dilute the liquid feed to the minimum suggested.
One generally fertilises at 10-day intervals but this is not to be regarded as exact; if the weatheris very wet and one continues to fertilise, it will tend to produce a lot of long sappy growth which will have to be removed from the tree. In this particular instance the fertiliser should be cut down to about every two to three weeks. Watching the tree and applying when it is necessary is much the best.
One can also use solid fertilisers, again organic, but as a lot of these tend to form moulds on the soils, or to give off an offensive smell, one will probably find that liquid feeding is the most convenient. If the tree is to be leaf cut (see notes on Training), it should be given a little more fertiliser for three weeks before and after it has been cut. One can also slow down the frequency of the application between the middle of May and the end of June as the trees should be growing vigorously during that period.
Soil
The tree might be beautifully trained but the effect will be greatly marred by careless treatment
of the soil surface. Moss should be encouraged to grow or planted at the time of re-potting. This
cuts down excessive evaporation from the soil surface during hot weather, and also stops the
soil being washed from the pot during heavy rain. However, it should be thinned out every few
months by pulling up a tuft here and there to stop the moss from becoming too packed. All
weeds, especially liverwort, should be removed immediately and any small under plantings of
rockery plants should be thinned out from time to time.
When adding compost be sure that it isn't too fine. If compost is too fine it then cakes up and
the Bonsai tree cannot get air and water to the roots. If this happens it can die. Try using a
scoop and sieve when applying the compost to avoid this potential problem.
Rotting leaves, twigs and general debris should be removed from the soil surface. Not only do
they look unsightly but they provide an excellent breeding ground for insects. Apart from moss,
one can also decorate the soil surface with small rocks, gravel, pebbles, etc.
Fungus and mildew
As with other plants Bonsai trees are subject to attack from fungus and mildew. They should
always be kept in a light airy position where there is plenty of air circulation and ventilation is
good. Immediately one sees either fungus, mildew, or rust on one's trees they should be treated
with a proprietary brand of fungicide mixed to the manufacturers' instructions.
Insects
All insects are not committed to the utter destruction of expensive bonsai trees. Ladybirds, for
instance, feed on the young of the aphids. In the soil centipedes-thin and yellowish with a host
of legs-are beneficial, whereas wireworms-thin and yellowish with few legs-are enemies; as are
millipedes-dark grey with many legs.
The insects to be discouraged above the soil are as follows: the Aphid family, green black and
woolly (usually seen feeding on the sap of young growth), mealy bugs (tiny scraps of cotton
wool in leaf axils), red spider (occasionally seen on warm days on the underside of leaves;
leaves attacked turn bronze and drop off), thrips (thunder bugs, small holes and silvery marks
on leaves), boring insects (the leopard moth is one; the pupal case might be seen adhering to
the trunk or branch attacked), leaf miners (silvery or irregular lines appear on leaves). Other
more easily recognised pests are caterpillars, slugs, snails, earwigs, etc.
Ants, worms and woodlice do not cause as much damage as the above but they should not be
encouraged. Ants disturb soil, encourage aphids, and remove seed from seed trays. They may
also disturb soil and block drainage holes. Woodlice live under debris and rubbish and attack
seedlings and young growth close to the ground. Neither worms nor woodlice are likely to attack trees if they are kept off the ground. Ants can be discouraged by immersing the whole tree in water for twenty-four hours. Fo rpsecific information on Pests and Insects try "The Art of Indoor Bonsai" or if you want to know which pests are attracted to which trees check out "The A-Z of Bonsai".
The best way of discouraging attacks by insects is to maintain the health of the trees and by
regular spraying with cold water during the Spring and Summer. Occasionally, however,
insecticides are needed, but when these are used they should always be applied at their
weakest to avoid damaging young growth.
Seasonal care and protection
Varieties of bonsai trees that come from tropical and sub tropical climates will have to be protected from even the slightest frost As such they can be kept indoors during the winter months, but they will benefit from periods outside during the summer.
Most trees from Japan are hardy and a light frost will not affect them at all. However, continuous severe frost will stop the translocation of water from the roots to the trunk and branches and might also fracture the pots. To avoid this some protection can be given (please refer to chapter on Display). If a display bench, such as the one described in the chapter on
Display, is used one should have little need to worry about the extremes of weather that occur throughout the year. However, always be on the lookout for excessively heavy rain, high wind, burning sun, snow, etc., and take the necessary precautions
to ensure the health of the trees.
Re-pottingWhen re-potting most plants one chooses a larger pot to allow for the expansion of the root ball.
When Bonsai trees are re-potted the same pot is used unless the tree has been allowed to
develop out of proportion to the pot. Generally speaking, trees should only be re-potted when
they have become pot-bound. In other words, the roots will have thoroughly penetrated the
compost and will be growing out of the drainage holes. If allowed to remain in this condition they will eventually die through simple starvation.
The best time for re-potting is in early Spring, through March and early April, though some trees such as Winter Jasmine can be re-potted at almost any time of the year. It is still safer to re-pot in the Spring just before the tree has started to grow. The materials used are (1) small pieces of plastic mesh to cover the drainage holes, (2) garden wire to tie the tree into the pot, (3) gravel or flint chips to act as drainage in the bottom of the pot, (4) sterilised sand, (5) peat and/or leaf mould, and (6) sterilised loam.
It is suggested that soil mixtures are made up for three basic types of trees: evergreens,
deciduous trees, fruiting and flowering trees. For evergreens a mixture seven parts sterilised
loam to three parts sharp sand is ideal. For deciduous trees, use eight parts sterilised loam to
two parts sharp sand. For fruiting and flowering trees, use eight parts sterilised loam, one part
sharp sand and one part peat or leaf mould. Naturally enough, for individual species in any
group, the suggested mixtures might have to be altered to a certain extent: Pines for instance,
need faster drainage than Junipers. Therefore an extra part sharp sand would be needed.
To remove the tree from the pot, run a sharp knife around the sides of the pot, knock the sides
of the pot with the heel of the hand; the tree can then be lifted from the pot. Clean the pot
completely, cut pieces of plastic netting to cover the drainage holes, insert the holding wires
through the holes, put a layer of flint chips or sterilised gravel on the bottom and a thin layer of
compost. Remove all dead roots from the tree and cut back the remaining roots from the sides
and the bottom by approximately one to two thirds. This will depend on the age of the tree: the
older it is the fewer roots are removed. Position the tree in the pot, moving it gently backwards
and forwards to ensure a firm grip with the soil underneath.
Tie the tree in with the wire (not too tight), pour the soil mixture in around the sides of the root ball until the pot is full up. Work the soil in around the roots with fingers or a small stick-this is to ensure that there are no air pockets. After putting in the main soil and tamping it down a thin layer of top soil can be used; this can be of a finer grade than that used in the main potting. The tree can then be watered by immersing it to the rim of the pot in a bowl of rain water. When it has been thoroughly soaked, remove it from the water, allow it to drain and protect it for two weeks from harsh sunlight and heavy rain. This will give it a chance to get over the shock of re-potting. During this time do not fertilise it at all. For detailed instructions on how to re-pot your bonsai see "The Art of Indoor Bonsai"
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