Elm-forest-by-Craig-1992I would like to go into this with a little more depth, as it is very important. One of the big killers of bonsai in incorrect watering. I am sometimes weary of people that still wish to immerse pots into buckets of water in every case or do not think it’s necessary to mist the foliage.  After nearly thirty years I probably manage the watering side fairly well – or at least my wife does these days, if I am  away teaching somewhere in the world.

The roots may become either dried or rotten because of too little water or too much water.

A free draining soil will assist in the transition of water through the pot. A compacted soil is obvious as water will collect on the surface. Ideally, when you water the Bonsai the water will flow freely through the soil.

Keep the soil moist in the summer but water less in winter. In winter just keep the soil damp and do not let it dry out.  Bonsai is not a cactus and needs a damp soil to keep the roots alive through its dormant period.

In most cool to temperate climates, watering once a day during the growing period is enough, but just check your soil. In hotter months watering will need to be done up to three times a day. If in a hot country, leave the trees in some shade for part of the day to keep the tree cooler. In some countries hot winds can also damage the tree by drying it out very quickly.

If your soils surface is looking a bit on the light coloured side it’s probably dry. However check just under the surface.

How to water your Bonsai.

Automatic watering systems are very popular and reasonably easy to set up.  Use a sequenced automatic time switch, sometimes called a ‘Computer Watering System’ but are really simple timers that start and shut off the water in a desired sequence.  This is good when you want to water some of the trees at a certain time and more than once a day in hot weather. You can rig up the hoses to a gadget sometimes called an octopus that has around six to eight hose attachment nipples and these can then be set to go off in a sequence that allows a different hose to water a different section, the next time the timer starts. It’s quite easy, as the timer can be set to go on and off six times through the day and if one section needs watering twice, then you attach a Y piece to two shorter hoses at different sides of the octopus.  Here is what I set up in my own place.

One and six waters the deciduous trees for 10 minutes each. The timer is set to 7am and 5pm.

Two comes on after one and waters the pines and conifers for six minutes in hot weather. Set for 4pm.

Three comes on after that and waters the Ficus and Willows etc –water loving plants, for 12 minutes. Set for 4.30pm

Four then comes on and waters the trees growing in beds, Yamadori etc. Set for 5pm

Five waters the rest of the garden plants and borders. Set for 5.30pm

If I need to water during the day in exceptional heat I can do so by hose without touching the Computer as the water faucet is rigged with a split tap to allow a separate hose connector.


The kit comprises a Water computer timer, a multiple hose distributor unit for six hoses and a water reducer that changes the flow from the hose into the narrower hose for the drip feeder nipples. I also use different nipples that allow different rates of water to travel through the feeder nipples from one litre an hour to ten litres an hour.

The one thing that is not good about auto systems is their reliability. The drip feeds can clog or stop working, battery powered ones are less reliable than mains powered, junctions in the piping may come apart when pressured up suddenly after softening in the sun on a warm day. They still water when the tree does not need any during rainy spells. Some systems I have looked at have a ‘cloudy day ‘ feature but it can be very warm on a cloudy day and the soil may still need water. Therefore, you are stuck between a rock and a hard place. You turn that feature off and the tree will be watered if it needs or does not need it.  Now all that is not too bad some of the time in a hot climate as the temperature is more than likely to be constant and so the trees will need watering anyway as rain would be rare in the warmer seasons. In humid climates the system is not so good of course. In any case the soil should be free draining and the water should run through fast of course. Use wooden wedges to tilt the Bonsai that need less water and will benefit from free runoff such as conifers.  Just ensure that the pot and wedge are secure and unlikely to topple of the bench. Alternatively, remove the drips from the pots every other day.

More expensive systems are available that have a sensor to determine moisture levels in the soil. Even these aren’t completely satisfactory, as one trees water needs may be radically different from another’s.

Automatic watering systems are not a great problem though and can be a benefit if you are off on vacation. The only thing you need to ask your neighbour is to just check that all the pots are being watered and that the soil is damp. Point out the potential weaknesses in the system and a good neighbour should manage.

Using a hose:

I still need to use a hose in other locations and I always attach an adjustable trigger spray or multi-spray unit to the hose. Water pressure is crucial here and if you have a lot of trees you will need to have a powerful spray that is still fine enough not to wash the soil out or damage the buds.

Hose spraying is most growers normal method of watering as this can be a more controlled way of making sure the right trees get what they need. Use the adjustable trigger spray to control intensity of water delivery. Feeder units that are supplied by most of the major plant food companies can also be added easily.  Just make sure that you do not overfeed. I prefer using pellet feed such as Biogold. This is a rather expensive Japanese food but is excellent at developing fine feeder roots.


Winter and summer watering.

This depends on the climate requirements.. Essentially you may water anywhere from once to three times in any one day. I would suggest that it may be better to water twice on a hot day and mist once or twice damping down the benching and ground to create some humidity around the Bonsai or Penjing. Not essential in cooler months. Essential for species that have fine needles like Junipers

Misting the foliage

Misting is giving the foliage a fine spray. While part of the general watering, spraying the foliage acts like rain. If you have warm days the foliage may dry up through dehydration. Misting will replenish the moisture in most cases. Extra misting can be very important in warmer climates, in hot weather and under shade net. Pine – Pinus need more misting that deciduous. Species outside India that are dense such as Cryptomeria and Sequoia need daily misting while others need misting every two or three days. Misting will clean the leaves, reduce pests and, as Chase Rosade the famous master once said, highlights the small webs of spider mite. Deciduous trees can trap water between the leaves and it’s therefore best to spray deciduous trees once a week or three times in hot weather. Water droplets will not act as magnifying glasses and burn the leaves. That is a myth. In colder climates, misting is rarely done in winter. In these cooler climates, the soil is kept just barely damp through the winter months. Many deciduous trees need very little light and water when under winter storage, though there is the danger of a tendency to forget all about them. Just remind yourself to check them at least once a week. I will reiterate that while misting is not the only watering given, it forms part of the general overall watering programme and if you grow tropical trees then you will need to mist two or three times a day.

Sub Tropical

This climate is more humid and while experiencing little colder weather, some cold days can still occur. The rainy season is generally more prevalent and the summers can be extremely hot. However, in many places the humidity levels can also be a factor in this climate.


Tropical. Mountains and lowlands

This climate does not experience cooler weather unless there are mountains where the cooler air can get to these peaks. I find that Bonsai and Penjing growers have seen changes in weather conditions recently that can be partially attributed to what is happening in warmer climates. I would like to discuss the general climatic changes that the globe is experiencing and comment on the results of these changes . I teach Bonsai  in many countries and I live in Scotland. We have seen a marked change in temperatures, humidity levels and rainfall over the most recent years. I am an avid photographer of landscapes and have been very fortunate to travel to many countries both as a Bonsai teacher and as a photographer. The reduction of natural habitat is in, my opinion, a very serious issue and we should be aware of the changes caused by deforestation around the world.

Deforestation is causing climate changes as is other factors. This means that temperate and cooler areas are having warmer, and sometimes wetter, weather than they had in previous years. Many very hot countries have high mountains such as Nepal with its vast mountainous terrain and deep jungles in the lowlands. In Africa, where the plains can be very dry in the summer months, Tanzania’s Mount Kilimanjaro, celebrated by Ernest Hemingway in “The Snows of the Kilimanjaro” have inspired many writers is, due to its altitude, permanently covered in snow. Climate is changing all the time but this particular ice cap will probably disappear by 2020 due to the deforestation of the lower slopes for pasture. This causes a change in the microclimate of the mountain. That indicator will mean that other mountains from across the globe with glacial ice caps will lose their ice caps if similar deforestation to create grazing areas at the mountains base happens elsewhere.
Using this analogy I remember my own Bonsai teacher talking about microclimates nearly thirty years ago and teaching us that each area, each bench and each pot can have its own microclimate. What you do to that tree can affect the trees microclimate. Understand the trees microclimate and you will understand what it is telling you. Short of talking to the trees, I suppose that learning everything about what affects us in climate and conditions is the only way that we will understand what the Bonsai are saying.

In the case of worldwide deforestation, this apparently could create higher temperatures in some parts of the world causing loss of ice caps, rising waters and in some cases more rain. We can do very little about these changes but we should be aware of the climate changes that may affect us in the short term. Recently we have seen some countries with exceptional storms, high winds, freezing winters, excessive rain and unusual weather patterns. Farmers in some temperate countries have lost crops through excessive rainfall.

Anything that I suggest in caring for your trees should therefore be read with the understanding that the weather really is beyond my control.

Article written by Craig Coussins©


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