The word Bonsai means ‘tree in a tray’ in Japanese.
Keeping the root environment healthy is essential when cultivating bonsai trees, and that means re-potting when the roots become overcrowded or the plant is still in the early stages of growth.
When choosing the media you should use the tree species as a guide and use a soil composition which replicates that in which it would grow in its natural habitat. Generally though a mix of equal parts loam, peat and sand would be fine. Alternatively, you can buy proprietary bonsai composts which will suit most species.
My bonsai is a Chinese Elm which has been in my family for nearly 20 years (no pressure to keep it healthy!). It has been a while since I re-potted it last, the roots are in need of trimming and the soil is depleted. Here I explain the simple process of re-potting it.
Soak the whole rootball until saturated.
Tease out the old soil from the roots.
Trim any excessively long roots.
Place a layer of fresh compost back in the tray before replacing the tree and gently dibbing in the fresh compost around the roots making sure there are no air pockets.
Water well with a rose.