Root pruning is the reduction of the root system that occurs during the periodic repotting of a bonsai. Pruning coarse roots helps the root system renew itself and become more dense. Fine roots are generally more efficient at absorbing water and nutrients than coarse roots, which primarily exist to anchor the plant and store energy in the form of starch. These are two functions that are not particularly important in bonsai culture.

Hi,
Are there any rules about how to Root prune your Bonsai? Some say that the roots should be no more than %30 bigger than the above ground section of the tree. Is that true?

One thing I've found is with training pots or just immiture plants, they need to spread out under the ground to get good taper on the trunk, or nebari of any kind. If your tree is under four years old, you should be probibly be at 200% root to get things properly situated undersoil.

Hello,

Root pruning is an integral part of bonsai. No plant can stay in a container indefinitely without some sort of root work. In this article I will discuss the mechanics and timing of root pruning for bonsai.
Plants are constantly in search of new water rich, nutrient rich material to grow their roots. In the earth this is no problem, roots can travel many tens of feet from the plant stem in search of nutrients and water.
If root bound plants are not top pruned they will quickly dry out on a hot day, requiring more than one watering per day.
he frequency of root pruning is related to a) the species, b) the container size, and c) the environment. The bottom line is that a bonsai should be root pruned and repotted when it shows symptoms of decline and/or chlorosis as described above, or when it begins to push out of the pot.
Root pruning damages a plant, restricting its ability to take up water and nutrients. Therefore it must be done at times of the year that the stresses on the plant are minimal. For temperate climate plants there are two times of the year that these conditions are optimal, late fall and early spring. Tropical plants can usually be root pruned and repotted during periods of 'quiescence' or slow growth.


Thanks.