Few aspects in the art of growing bonsai are as tenuous as watering. Many a bonsai tree has been killed by overwatering, and vice versa. You might say that watering bonsai is an art in itself that requires experience; it may require a couple of years, and some trial and error to get this thing right.
Among the elite bonsai masters in Japan, they do not even allow their apprentices to water their trees! You might think watering is such an easy thing to do, but, in bonsai growing it makes a lot of difference. Most shops will tell you to water your bonsai “once every few days”, but such vague instructions are next to useless, as there are many aspects pertaining to watering that in themselves require further study, such as species’ requirements, weather, temperature, the condition of the soil and even the age of the tree.
Bonsai soil is quite different from your standard potting soil. By design, it is porous and provides very rapid drainage. So what you need is to water enough, so that the soil stays moist, but not too moist until root rot and the growth of fungus and mold occur.
Over time, you should develop your own methods on how to test the soil moisture level and also develop a sense on how much water is needed each time. In fact your watering education starts the moment you bring home your first bonsai!
For a fast check, touch the surface with your thumb. If it feels dry, it is. Gently scrape back any ground cover, gravel or surface earth to perform a better check. A more accurate test can be accomplished easily by using a standard moisture gauge. Often looking like an ordinary thermometer, analog or digital displays will provide a much more accurate reading.
The moisture in the soil is largely dependent on external humidity levels. Even though the soil may be wet hours after you watered, if the weather is going to be dry and windy for the next couple of days, you’ll be surprised just how fast the soil will dry up.
External instruments can only gauge the moisture level since they only detect water near the tip. Dry spots can occur anywhere within the pot over time, since roots may cluster in certain zones within the soil and interfere with proper irrigation. As such, if dry spots occur around the roots, it can lead to die-back of certain portions of the root system. As your bonsai tree’s roots are always growing and developing, be aware that dry zones can appear gradually over time in your pot.
To ensure that the entire soil is adequately moistened, once a month dip the pot up to the base of the tree into a bucket or sink filled with water. Let the pot absorb water for a few minutes, then carefully remove by lifting the pot up with your hands. Do not ever lift the pot by grasping the trunk and heaving; you could uproot your bonsai tree or damage the delicate root system.
To be continued in part two.