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General care of bonsai

Bonsai training is an ancient art which had been practised for thousands of years mainly by the Chinese and Japanese and is now extremely popular with many people practising this ‘living’ art in its many forms.

Training bonsai takes many years and is achieved by pruning and wiring of roots and branches to maintain the bonsai in a ‘restricted’ condition, and to produce a tree which creates a feeling of great age and beauty.


This is carried out continuously throughout the year mainly in the summer and autumn but often depends at what stage the tree is in initially.  Newly planted bonsai are often pruned in the spring prior to potting, and later on in the year again to maintain shape.

Summer pruning is carried out to maintain shape and to encourage back budding to develop in about June and July, and once again in late autumn if required.  Some species may be pruned only and not wired to create their shape, and trees such as Japanese maples which have very brittle branches can be guyed down with wire instead to prevent scarring. Japanese maples are often leaf pruned as well to help produce a second crop of smaller leaves more in scale to the tree.

When training thinner shoots into new branches emanating from the trunk, these should be allowed to grow feely and should not be pruned as these will thicken quicker and the branch should be left to grow unchecked. As the branch gets thicker over two years or so, the branch can be guyed down or wired into place at a later stage and the end pruned back gradually to produce back budding.


This operation is usually carried out in the autumn and winter in order to train branches into their set positions, but it can also be done in the spring and summer if necessary as the branches are more supple with sap and are a lot more flexible.  The wire can be left on for about six to eight months or until the branch swells and just before the wire starts to mark the bark.  The wire must then be removed before ‘scarring’ occurs.

When training three to four year-old trees, the trunk shape must be set first of all before the side branches are wired.  This operation usually takes a year to complete, and once set some of the side branches can be wired in one go.  Always use one piece of aluminium or copper wire to set two branches at once.  This saves on wire and later it can be carefully removed and possibly used again.  Note:  Do not wire too much of the tree in one go because this will over-stress the tree and may kill it.

Once the branches have been set, remove all wire except where new branches are still being trained into position.

Watering and feeding

During the spring the bonsai must be checked daily to see how dry the compost is and thoroughly soaked if very dry.

In about April and May start application of liquid feed through the hose system or by watering can and continue throughout the summer, once every two weeks.  Use a liquid feed like MiracleGro or Levingtons feed which have relatively low nitrogen analysis or a balance of NPK.

For longer term feeding, organic fertilizers such as pelleted chicken manure or comfrey tablets can be used to increase the nitrogen, and this can be applied around the base of the bonsai and left to break down naturally during the summer.

All bonsai are extremely susceptible to drying out in hot, dry and windy weather because of the small root system space, and they must be checked and watered daily or every other day in spring, summer and autumn.

In September switch to a high potassium and phosphate and low nitrogen fertilizer such as Phostrogen or Chempak No.8 which will reduce any sappy growth and help to harden off the branches ready for the winter.  Continue to water daily as and when necessary.

In winter under normal conditions, there is usually enough rain and dampness in the air to render watering unnecessary; however when the weather is exceptionally mild and dry, watering should be carried out in order to thoroughly wet the compost about once a week.

Potting and repotting

Established outdoor bonsai require repotting every three to five years to maintain health and vigour, and before this operation is carried out all the roots must be teased out and at least one third of the roots trimmed off. Any crossing roots that cannot be trained in , and any dead roots must be removed. Root pruning encourages the regeneration of fibrous roots which will eventually fill the pot completely.  No feeding should be necessary for the first year after repoting.

Newly trained bonsai must have an adequate fibrous root system before potting and at least one third of the roots may need to be trimmed so that the root system fits into the required pot.

If the bonsai is being potted into an unglazed or glazed bonsai pot, the tree should be positioned correctly into the most appropriate pot in scale to the tree, and always wired in to give full stability until the roots have become established.

The plant at this stage can be raised up further in the pot if so desired to expose more of the root structure, and to increase the interest of the trunk shape.


These should be relatively free draining so the tree roots can breathe, and also so the compost does not get over wet in the winter months.

For broad-leaved deciduous trees and evergreen trees (such as Holly, Box and Evergreen Oak):

  • One part peat free compost or bark
  • Two parts clay loam, Akadama or Biosorb(Neutral or alkaline

For conifers and ericaceous plants:

  • 100%  Kanuma (for ericaceous plants only)
  • Two parts peat free composted bark and Akadama
  • 1 part clay loam (acidic)
  • One-quarter part sharp washed sand or grit


In the early stages of training, young bonsai can be grown in ‘trainer’ pots which help the root system develop in the right way.  At a later stage it can be repotted into a proper glazed or unglazed bonsai pot which must be frost-resistant.

It is important that the pot is of the right type and colour so the tree looks in the right proportion to the pot, and also it must also be located in the pot so that it looks balanced.

All bonsai have a ‘front’ and a ‘back’ and the plant and pot must be viewed from the front as one (especially for exhibition purposes).

Pests and disease

All bonsai are susceptible to pests and diseases like any other plants and will show the same symptoms on the leaves, flowers, stem or roots.

Bonsai plants must be inspected regularly for any signs of pests and diseases, and must be treated with the appropriate insecticide or fungicide as soon as it is detected.  In most cases, pest like aphids, woolly aphids, mealy bugs and scale insects can easily be seen and should either be removed physically by hand, sprayed or dunked in a solution of a systemic insecticide.  Repeat treatments every month as necessary.

Other problem pests include vine weevil larvae which occur in the soil as small white grubs which eat the roots of seedlings and established trees.  These must be controlled as soon as they are seen either with a root drench of Gamma HCH or ‘Provado’ once a month or a biological control such as Nemasys-H.  The adult vine weevils eat leaves by cutting out holes and semi-circles, and are best caught at night on the plants and destroyed.

Another soil living pest is the leather jacket which is the larvae of the crane fly.  Again use a soil drench of Gamma HCH or ‘Provado’ once a month if seen in the soil.

Fungal diseases such as powdery and downy mildews, wilts and rusts tend to occur on the leaves of deciduous trees and occasionally on evergreens, and should be treated with a systemic fungicide as soon as it is detected.  Also maintain a humid atmosphere around the plant by regular watering and spraying which helps to control this disease.

Japanese maple bonsai and other young maples should be watered or dunked in a solution of systemic fungicide twice a year to prevent die back and infection by Phytophora and fungal pathogens.


The site provides information on the history of bonsai, different species and how to propagate them, and details of workshops on the art of bonsai growing and the care of bonsai, trees for sale, and of a re-potting service.
©2010 Colin Carpenter