There is a saying in Japan that it takes three years to learn to water correctly, and while some might scoff at such a statement, ask any longtime bonsai enthusiast how long it took for them to begin to have real success at keeping their bonsai alive. Odds are it was about 3 years and the early failures were probably due to improper watering practices.

The information that follows in this article assumes that your trees are planted in bonsai soil, not just dirt or potting soil and that there are no root-zone problems which might interfere with the uptake of moisture from the soil.

"Bonsai ni ame ga ni do furimasu"

- For bonsai, it rains two times.

The above is a Japanese adage for watering bonsai. It speaks to the need for proper, complete soil saturation at watering time. Why should we water two times? Well, how we want the soil and water to interact and how they actually interact may not always be consistent. When dry, many soil components tend to shun water, especially large volumes of water and this characteristic can cause bad things to happen in the pot. For instance, if you just dump a large quantity of water on the soil, the water will seek the route of least resistance which often means forming channels through the soil and poring right through to the bottom and out of the drain holes without a root being touched or the soil being saturated. If you never change your watering method, these same channels are used each time and your tree will decline and, perhaps, die.

To get proper soil saturation, you need to first wet the soil a little so that it will better accept the water. After that, you may water thoroughly to saturate the soil. This ensures that the entire root pad gets wet. If your whole root pad doesn't get wet each time you water, you will risk having root rot and dieback with a corresponding foliage deterioration.

Over-watering :

Often, one of the first caveats we get when starting out in bonsai is "do not over-water." Most might interpret this admonition to mean that we should just "moisten" the soil and not soak it. This is, however, not correct. Each time you water, you should fully soak the soil. Over-watering is what happens when the soil is not allowed to dry out due to too-frequent watering. This makes the soil inhospitable for the tree as it prevents enough oxygen from reaching the roots and promotes the growth of fungus and other pathogens.

Water behavior :

Pay attention to how the water first behaves when it gets on the soil. If it just sits there or runs off the soil and over the side of the pot, you need to do something about it. Many fertilizers, especially organic cakes, can break down to seal the surface of the soil, even coarse soil. If this has occurred, take a chopstick and "chop up" the surface of the soil, down about 3 or 4 cm.. This will allow the water to better penetrate the soil and saturate the whole volume. 

Get to know your trees :

Do you use a watering can to water by hand or do you have a timed, automatic system or do you just use a watering hose with a sprayer? I will suggest that you water each of your trees by hand with a watering can. Yes, I know this is a time consuming task and it's often hot outside, etc..., but if you do not water by hand, I doubt that you really know what's going on with your trees. Watering by hand with a watering can affords you the opportunity (once, twice or or more times a day!) to have a good look at each tree and keep tabs on what's going on with each one. It is usually the case that those who use an automatic system have more tree health problems than those who water by hand. Pests invade the trees, fungi attack, birds dig out the soil, wind blows trees over, cats jump onto them and break branches, wire bites into the bark due to fast growth,... all of these things happen on a regular basis and if you don't see your trees each day you will miss the opportunity to fix the problem before it causes a greater one. This is not to say that watering by hand replaces the need to closely examine each tree on a regular basis, but it does positively augment that necessary task.

Watering by hand allows you to give specific watering care to each and every tree and do so in a manner that is consistent with the specific needs of each tree. For instance, some trees like to have an overhead sprinkle while others need to stay dry on top and just have the soil watered. Some need to be watered very little while others more often. Some like a quite low ph water and others enjoy a more neutral ph. Most watering systems do not afford you the chance to individualize your care for each tree. While some bonsai growers do just fine with watering systems, your chances for having robust, healthy, happy trees are increased greatly if you water by hand.

So, in a nutshell:

• water by hand and have a good look at your trees each day.
• watch the water on the soil - it should pour right through and not just in places.
• water at least twice for each tree.
• give each tree the specific kind of watering care it needs - (less often, more often, soil only, foliage sprinkle, low or neutral ph,...)

Following these guidelines may go a long way toward improving the health and quality of your bonsai.