Pruning the leaves and root pruning is essential to the wellbeing of your bonsai tree. Leaf pruning gives the tree shape and root pruning allows the tree to grow healthily.
Pruning: To prune correctly you must find out the type of bonsai your tree is and when the best times are to prune old and new season growth. Pruning is the removal of branches from last year’s growth for creating or cleaning up the look of the tree. It also keeps it to its miniaturized state, without pruning it would grow into a full-grown tree. In general remove branches growing straight up, straight down or branches growing parallel to other branches plus any dead branches that there may be. When cutting entire branches, it is best to use a concave cutter at the base of the branch leaving a small collar protruding, this will leave the cut less noticeable when it grows.
The top of the tree grows faster so needs pruning more often to maintain the shape of the tree it should reflect on the shape of the trunk.
Root pruning is a major part of growing bonsai. No plant can continually live in a container without having its roots trimmed at some stage. Plants are constantly looking for nutrients, in the earth their roots can grow tens of feet but when kept in pots they saturate the pot with roots and become root bound and sometimes even push the plant out of the pot. The idea is to keep the tree moisturized so you should prune the roots then return it to the same sized pot with new soil. Root pruning reduces a trees ability to get water and nutrients so should be done when it is not in its growth period. The normal time is late spring depending on what type of tree it is.
Buds on a tree contain enough food to still open if the roots can get enough water to them, this allows a period of time to manipulate the roots without the plant suffering too much.
Root pruning is very simple to do, just unpot the plant and straighten and untangle the roots. There is a tool you can use for this called a “root hook” which minimizes any damage done. Start at the edge and gradually work around. You want to keep the main thicker roots so try to comb out the smaller roots rather than pulling them out. You should cut the thicker roots and keep the smaller spindlier roots as these are very good at absorbing water which the tree will need after pruning. To be on the safe side do not cut more than two thirds of the roots. Then repot with new soil and water, it will need watering more often to begin with than normal.
Depending on the type of tree you have it may take a time for the tree to recover from pruning as some trees take better to pruning than others.