As is true with all trees, trimming is important. It is especially important with bonsai trees, since they are known for their beauty that comes through careful trimming. Plan trimming thoughtfully in order to ensure the bonsai tree becomes a work of art.
Gardeners new to bonsai trees may feel stressed when they first begin to trim a tree. It is important to remember that trees do grow and therefore all trimming mistakes are fixed over time. This understanding removes much of the initial anxiety about trimming bonsai trees.
Time trimming carefully. It is crucial to trim bonsai trees during dormant seasons, when the sap does not rise. The dormant season is different for different types of bonsai trees. For example, deciduous trees should ideally be trimmed in early spring or late winter; pine trees should be trimmed in the fall; and the best time to trim junipers is in the winter or early spring.
Trim the roots. People trim bonsai trees to create precise and beautiful shapes, but trimming the roots is foundational to the overall health and beauty of the tree.
Dislodge the soil from around the roots using a root hook. Trim back the longest roots as well as roots that grow down rather than horizontally.
Trim off all branches that are on the lower third of the plant. At this point trim only the branches that are in the front of the tree. The bottom portion of the trunk is beautiful in itself and should be part of the overall design of the tree.
Trim branches that are opposite each other so they end up being the same size. Though shorter branches may be trimmed some, focus on trimming back longer branches so they are similar in length to the branches across from them.
Seal larger cuts. Though it is unnecessary to seal cuts when twigs are severed, it's important to seal cuts when branches are trimmed off of bonsai trees. Japanese wood-cut paste is a good option for all types of bonsai trees; tar-based bonsai paint is ideal on deciduous trees; and grafting wax should be used on evergreen trees.