To a thread at bonsai talk overwatering myth
I wrote this:
The subject is close to my heart since many years. Bonsai don't die of root-rot. The roots of bonsai die because of some problem, then people continue to water as before. The roots cannot take up the water because they are dead. The soil or substrate as a consequence becomes more moist than before. The tree shows signs of death. The bonsai is taken out of the container and it is clear that the roots are rotting. One can see it and one can even smell it. Also it is obvious that the soil is too wet. So the gardener comes to the conclusion that the tree was overwatered and died of root-rot.
The roots have rotted because they were dead. Trees don't die of root-rot like people don't die of FEVER. Fever is a symptom of a disease. It can be many different diseases but the symptom is the same. Root-rot is a symptom and can have many different reasons.
In general bonsai are UNDERWATERED most of the time. Our literature warns so much of overwatering that most bonsai folks underwater their darlings. Many trees suffer or even die because they are not watered enough.
Modern substrates have created a very different situation than what is described in most bonsai books. What is a modern substrate? Well, anything like akadama, pumice, crushed lave, baked loam, turface, Styrofoam flakes, coconut crush, seramins and hundreds of other materials. They all have a couple of properties in common: small particles of even size which don't decompose or decompose slowly; ability to work as water buffer - take on water and and release it alter; due to the coarseness drainage is good and aeration; OXYGEN gets to the roots easily.
Consequences if you use modern substrates:
1) You MUST water aggressively and frequently. Meaning everything must be wet whenever it is time to water. During the main vegetation period this is EVERY day. Overwatering is not an issue! It is not possible to overwater. Whatever is too much will flow out of the pot through the drainage holes. Underwatering is very well possible.ANY FOOL CAN WATER WELL! Al that one has to do is to maike eveything dripping wet. If al trees are in modern substrate ther is no such thing as individula wateing anymore!
2) Yo MUST feed aggressively and frequently. During the active vegetation period this means about every ten days to tow weeks. You should feed much more than you used to. I feed about 30 (thirty) times more than I used do in the old days when we used soil instead of substrate. You can use chemical fertilizer. The danger of chemical fertilize (namely burning roots) is not present when you water aggressively. Whatever is too much will be washed out soon. You should use organic fertilizer a couple of times during the vegetation period besides chemical. Organic is everything that smells. (BTW: it is absolutely NOT necessary to use feed cakes and to mix you own feed. Any agricultural store has everything you need for bonsai.)
As a result your trees will grow much better than they used to.
I treat all my trees including ALL my world famous trees exactly in this way. I water about 500 trees in 30 minutes. Or my wife does when I am not there. She has no clue what she is watering. And she does not need to have a clue.
Don't trust you literature! Most bonsai books were written long before we started to use modern substrates. The information in bonsai books about watering, feeding, soil is antiquated most of the time. The information is even very dangerous if you use modern substrate.