For those of us living in the Western Cape, just when we thought winter was nearing an end it started raining again. When it rains like this, almost continuously for days on end I wonder how many of us consider what is happening in our bonsai pots?
Shallow containers retain much more water than deeper containers. Sounds like a contradiction I know, but its the truth.
This is one of the practical reasons why we plant trees such as pines which don't like wet roots into deep containers and trees such as maples which quite like the water in shallow ones. If you were to water a tree in a shallow container and then after some hours lift it from the pot, you will note that on the bottom of the pot water will have collected in a pool. This is not related to a poor quality pot or anything of the sort just that water will puddle in the depressions.
During the active growing period when roots are taking up this water, its not much of a concern however when you have just repotted and it rains day after day it is a problem as there is little demand for water. Its also a problem when during the rainy season the containers are not able to dry out and the roots effectively just sit in water - drowning!
Now to the point of this blog post; a really simple way to alleviate the problem is simply to elevate one side of the pot with anything lying around, a piece of wood is what I use. This causes the water to accumulate to one side of the pot, assisted by gravity, and run out the drainage holes in so doing. Some water might still collect on that side of the pot however the roots everywhere else will be "high and dry." You can remove the wedge when rain has let up and the sun is shining. However generally when using shallow pots you should take care when watering. If watering by hand you can simply skip a tree if you see the soil has still not dried sufficiently, however if you use an automated irrigation system then elevating one side of the pot might be a permanent fixture for you.