Watering

A tree developing in its natural surroundings needs a considerable amount of water, which it obtains by developing deep roots which stretch far into the ground. A bonsai has similar requirements in proportion to its size. In other words, most bonsai need frequent and copious watering, particularly in summer. The fact that most bonsai are kept outside and exposed to the rain does not mean that one can dispense with watering since the moisture held by the root ball is always inadequate.

Water

Like other trees, bonsai need fresh water, free from toxic physical or chemical elements. Of course, the best water is rainwater, even though it may be polluted in towns. Well water is also suitable, provided it is not hard (i.e. limy), in which case water softening equipment should be used. Alternatively water softening tablets which are offered for sale can be added according to the instructions on the packaging to 'soften' the water by reducing the pH.

Tap water should only be used if relatively free from chemicals used in the purification process. The main danger is from chlorine, which is highly toxic to plants. If there is no alternative, keep the water outside in the open for several days, in which time much of the chlorine should evaporate. Whatever water you use - particularly if it is well water - make sure it is not too cold or it could give bonsai a shock. It is a good idea to fill your watering can several hours before use, so the water can warm to the temperature of its surroundings.

How to water

Always water bonsai with a fine rose so you do not damage the delicate leaves or wash away the surface compost. If you only have a few plants a watering can with a fine rose will do. If you have a collection of some size, watering may become a major chore and you will need sprinklers, operated mechanically by a tap or automatically by an electronically controlled valve.

As well as a watering can, you will need a sprayer, preferably a pressure sprayer, for misting over the leaves during warm weather. However, a sprinkler device will do this for you automatically.

It is impossible to say exactly how often bonsai should be watered, since each species has different requirements and climatic conditions may also vary. As a general rule of thumb, water often and sparingly, rather than occasionally and generously. The compost should be moist but not waterlogged. Any retention of water may set up root rot.

It is important to realize that bonsai require most water when growing most vigorously and in hot weather, and that less water is required in the weeks following root pruning, and clipping of shoots and leaves. This is because the reduced root system draws in less water and less is evaporated from the leaves.

In general terms, trees should be watered about once a week in winter, although this will depend on the overall humidity, and several times a day in midsummer. If the root ball dries right out, the tray should immediately be immersed in a basin of water. If you have to do this, be careful that the tree does not become uprooted. You should also damp over the foliage. It is especially important to look at the tree on a daily basis as the spring - and hence warmer weather - approaches.

Too much water can also be detrimental to the tree. For outdoor bonsai the heavy autumn and spring rains can be just as damaging as the hot summer sun. To stop the soil becoming waterlogged, place a sloping shelter, such as a sheet of clear plastic or polythene, over the trees, or angling the trays slightly, so that excess water runs away on its own.

If the tray is left on a slant, watch that this does not result in the tree growing out of shape. Apart from water-loving trees such as wisteria and willow, do not stand the container in a tray or saucer, as this could stop water draining away and cause root rot.

Watering indoor bonsai poses fewer problems, since the indoor climate remains more or less stable. Water them at least once or twice a week, depending on the size of the pot (the smaller it is, the more often you will have to water it).

The bonsai leaves should be misted over with water frequently as the atmosphere can be very dry indoors. Central heating aggravates the problem, and you will find it necessary to spray even more frequently, especially in spring, when the growing season starts and often the heating is still on.