Trees in free nature are able to survive longer periods without water. Regularly, there is a period without rainfall for trees, which make their roots go in search of water and feeding substances, not being limited by a bonsai pot. By placing a tree in a pot, the roots have been limited in their search of water and feeding substances. To give water in the correct quantity, which provides in the requirements of the tree type, you need a lot of exercise. Some bonsai masters even say that giving water to bonsai is one of the most difficult techniques to learn in bonsai. And because your bonsai’s health depends on it, you should give it the proper attention.

The most frequent asked question around this is: "When should I give water to my bonsai?". Although experience plays a large role here, it is very important to observe your plant regularly. Do the shoots hang weak, or not? Is the foliage healthy-green, or does it seem dull? The soil in the pot certainly is a good indicator here. Feel the soil with your fingers, to indicate how wet it senses. After some time you will learn the needs of your tree, just by feeling the soil. Even the weight of a pot can tell you much concerning the quantity of water in it. The need for water depends on many factors, like the type of tree, the age, the size, the soil mixture, where it is positioned, the format of the pot, the season and the type of weather. By observing this well you learn to know the water-household of your trees.

In the summer, when it is hot and dry, sometimes it is necessary to give water a few times a day. Best time to give water is in the morning, or in the early evening. Avoid giving water during the afternoon hours when it’s warm. During the water gift on hot summer days, you can thoroughly moisture everything around your bonsai as well. When you do this, you will create a wet microclimate around your trees, and your trees will appreciate this. During the winter, when trees become less active, they will also consume less water. Do not give water when it freezes. Check the soil for being frozen, and wait until it thaws, before giving water. In periods with long-term rainfall, it is appropriate to protect the trees for abundant rainfall. Pay attention for drying out winds. A firm wind can dry out a pot on a relatively short period of time. Giving too much water is a just as large problem as giving too little water. Too little water, and the tree will dry out. With too much water there is the risk of rotting roots. The internodes (distance between the buds) will become longer, and the tree becomes weaker. Especially pines and some other conifers are very sensitive for this. For this reason you will always need a good draining soil mixture. If you give water, water must sink immediately. It certainly may not 'stand', because that indicates on bad drainage. Roots need water, but the water must be able to swiftly flow away. Each time you give water, the air between the ground is refreshened, and redundant salts are washed away. Therefore you should give sufficient water each time you give water. If you only moisture the surface, the tree will respond with rooting only in the top-layer of the pot. Trees with a top-layer root-system dry out very rapidly, and make the tree weak. Because roots are searching for water, the complete soil in the pot should be wet, each time you give water. Only then a tree will create a good developed root-system. So you better split up each water gift in several turns. You firstly sprinkle the surface so that it becomes well permeable. Do this with all your trees. When you are finished, you start again giving water once more to each tree, and then you should give sufficient water, so that the water flows out abundantly from the drainage holes of the pot. If needed, you can do this once more, a third time with all your trees, to be sure all the soil has become completely wet. Pay attention with rainy weather, because one is rapidly tended to think that during rainfall no more water gift is necessary. Trees with a dense canopy lead rain water outside the pot. In spite of that the tree nevertheless looks wet, it is possible that there is insufficient water present in the pot. From time to time, you can place a tree in a water-bath. This way, you are certain that the soil is thoroughly watered. When air stops bubbling up from the soil, this can lasts sometimes up to 4 -5 minutes, you can be sure your soil has been well satisfied with water. Also the air between the soil-particles has been entirely refreshened. If you don't see bubbles coming up when immersing, then there is something very wrong with your soil-composition. The soil has become silted up, and repotting will be necessary. Most trees appreciate it, if their leaves or needles are sprinkled with water. Dust on leaves and needles are washed away this way, and it helps the tree improve to breathe. However, pay attention for your type of water, because hard water can leave behind white deposit on your foliage.

Which water you should use, depends on the circumstances. Rainwater is generally the best to use. Yet by acid rain and air pollution you should nevertheless watch out with it. People who live in the vicinity of industrial areas, or in big cities with much traffic, should look for other means. It is possible to measure acidification or pollution of rain water with measure-sets. Be very suspicious, if you find a dirty greasy film floating on the water surface. This almost certain indicates on pollution. You can collect rainwater in a fixed rain water well. Also you can use a barrel placed under an outlet pipe of the gutters, or just a big ornamental pot. Tap water and well water are sometimes dissuaded because it contains too much calcium and chlorine. You still can use this water, dependent on the type of your soil mixture. If you keep this water 24 hours standing in a tank, chlorine will disappear. Only use pond-water, river-water or ditchwater, if you are completely certain that there is no pollution. Bottle water is also possible, but in the long run very expensive.

When giving water, you should realize in which phase of development your tree is. Because giving water and fertilisation cooperate, you should give a young tree, which must grow still strongly, more water as a bonsai, of which you want to preserve the form as much as possible. You don't need exuberant increase in growth with such trees. Always keep the seasons in mind. In spring, when the growth-speed is at his highest level, the trees will consume more water than in the late autumn when the growth comes to a stop. Of course, the species are also very important. A willow tree needs much more water than for example a pine. Learn the water need from your tree-species, to avoid problems afterwards. Also be very carefull after total leaf-removal, because the tree doesn't have it's leaves anymore to evaporte water. Always use a watering can with a fine hose, so you don't wash away soil from the pots.

For species who are sensitive for moulds such as mildew, for example oaks and field-maples, you should prefer to give only water in the morning. The foliage has then already dried if it becomes warmer. If you give water in the evening, and the foliage stays wet at night, the better conditions (warmth and humidity) for moulds arise to develop. Look for somebody with the proper knowledge about giving water to bonsai and take care of your trees, when you leave your home for more than a few days or more. It will not be the first time that a neighbour man, or a family member, ruins a tree out if pure ignorance.

Finally, I want to give you the advise to check the drainage holes regularly. Roots which grow in the drainage gauze can block the drainage, which can have a funeste impact. I think if you follow these rules, you are in the good direction with giving water to bonsai. Because the health of your tree is determinated mainly by giving water, you should do this in the most apppropiate way.

(Author: Hans Vleugels)