Preferential Pathways in Bonsai soil
Preferential Pathways PDF Print E-mail
Written by Bonsai King   
Saturday, 21 June 2008 18:47

The path of water as it goes through the soil is not even all the time. If the soil mix is not right or if the soil has compacted due to time, preferential path ways for water will develop. This is a very important matter that is often overlooked. You must understand that confining a tree in a pot provides a very small volume of space for the roots to develop. To support healthy thick foliage the number of fine roots has to be maximized. To do this the whole space of the pot must be filled with fine roots. The long thick roots that you see are just structural it doesn’t help in the nourishment of the tree; the fine roots are more important because these are the ones that take up water and nutrients.


The diagram below shows a compacted soil showing the preferential path of water thru the sides of the pot. Notice that the dead zone is at the center beneath the tree, while the live zone is near the path of water. The roots within the dead zone are just structural in nature while the roots that are in the live zone are the fine roots that take up water and nutrients. From the diagram, you can see that the actual volume of the pot was reduced due to the dead zone. This is like putting your bonsai into a much smaller pot. This is very bad for your bonsai.

bonsai bonsai


A lot of bonsai fatalities occur when people follow the advise of trimming the roots one inch from the walls of the pot during repotting. Yes, this can be done on a bonsai with healthy roots but for cases such as this where the live part is only at the walls of the pot, death may occur. For a bonsai to reach its full potential, dead zones has to be avoided at all costs. Be very careful in choosing your soil mix and be observant on the condition of the soil as time goes on. The pot shown above is a regular pot. An actual bonsai pot is very shallow (why?) as seen below. Just imagine how small the live zone has become.

bonsai bonsai


When the pot easily fills with water and takes a considerable amount of time before the water drains, this is a warning of bad soil condition and the soil has to be replaced. When the soil doesn’t drain, it means that the soils is compacted and the path way to the bottom drain are few and narrow that it takes a lot of time to drain.

As advised by a lot of books and websites "leave a ball of soil when re potting" . In this condition it makes no sense at all, as the ball of soil contains no live fine roots. If you encounter problems like this, remove all the old soil by immersing it in water and gradually remove the soil by your hands taking care not to damage the fine roots. This called bare rooting. Repot in a larger container using a good soil mix first then let grow for some time before prunning the roots and repotting to the same pot. Be sure to use the right soil mix this time and each time

Last Updated on Sunday, 22 November 2009 23:20