The time of pruning bonsai depends on the type of bonsai tree and also the location where it is kept (indoor or outdoor). For example, late winter is a good time to perform maintenance pruning on broad leaf trees. On the other hand, conifer trees are best pruned in late fall (except Juniper trees-These trees prefer pruning in late summer)
Checkout bonsai tree pruning to know more about how to prune a bonsai tree.
The process of pruning trees that experience seasonal changes in temperatures and day length (deciduous trees) generally involves two phases.
Minor maintenance pruning: You can perform leaf pruning and pruning of new growth on deciduous trees at any time during the growing season.
Hard structural pruning: If you are intending to perform heavy branch pruning where you will remove large branches also, do this in the dormant season (winter season). Deciduous trees are not in active growth at this time of the year. Sap in the trees is not flowing, so you do not have to worry about the tree bleeding through the pruning wound.
On the other hand, trees that have tropical and subtropical origins don’t require pruning to be done in phases. It is generally possible to perform heavy branch pruning as well as general pruning throughout the year. This is because tropical and subtropical trees do not undergo disruptions in their growth like deciduous trees. They do experience a shortish period of dormancy, when their growth is slightly reduced, however it is not as severe as that experienced by deciduous trees.
As a general rule, the best time to prune an outdoor bonsai tree is in the spring, when the tree is active and healing can begin immediately. Indoor bonsai tree can be pruned at any time of the year. This is because hardy outdoor bonsai trees go dormant for about four-five months of the year. While the growth of tropical indoor bonsai trees is relatively constant. (You can slow down the growth of these indoor bonsai trees by exposing them to lower light levels in the winter)
Performing bonsai pruning in the fall may result in the die-back of the bark surrounding the pruning wound.
Performing bonsai pruning in summer will lead to the rapid growth of unwanted shoots from around the pruning wound.
By pruning the bonsai tree in late winter or early spring, their form can be clearly seen. Pruning bonsai trees in the winter will be more effective if they are protected from the elements.
Please read types of bonsai trees to know more about the pruning time and frequency of a particular bonsai tree.
Some examples of when to prune a specific bonsai tree
(1) Japanese Black pine bonsai (Pinus thunbergii) : Pruning of shoots can be done early to mid summer.
(2) Spruce bonsai (Picea) : Perform pruning as the shoots appear. Prune away almost half (2cm) of length from all the shoots.
(3) Chinese juniper bonsai (Juniperus chinensis) : Prune from spring to fall. Pinch almost all the shoots.
(4) Needle Juniper bonsai (Juniperus rigida) : Prune the bonsai as the new buds appear. Debud the tree completely.
(5) Maple bonsai (Acer spp.) : Pruning can be done from spring to late summer. Prune the leaves, leaving one pair of leaves. Also remove the buds.
(6) Elm bonsai (Ulmus spp.) : Pruning can be performed from spring to late summer. Prune the leaves, leaving one pair of leaves. Also remove the buds.
(7) Beech bonsai (Fagus spp.) : Pruning can be performed from spring to late summer. Prune branches and leaves leaving one to two pairs.
(8) Firethorn bonsai (Pyracantha) : Prune the tree in mid spring. Pinch back the new shoots.
(9) Fruiting bonsai : Prune these trees in mid summer. Pinch back the new shoots.
How often to prune bonsai
The frequency of pruning a bonsai tree depends on the bonsai tree species and the rate at which it grows.
It is usually necessary to prune deciduous trees 2-4 times a year in order to keep them in good shape. On the other hand, since evergreen bonsai trees aren’t as vigorous as deciduous trees, they don’t require pruning as often.
The growth rate of deciduous trees is usually considerably higher than that of evergreen conifers. Their new shoots extend fairly quickly.
What happens if you don’t trim a bonsai tree?
If the bonsai tree is not trimmed or pruned it will not only look unsightly and unkept, but also the risk of death of branches (or even whole bonsai tree) increases immensely.
The whole idea of creating a bonsai is to create an aesthetic miniature tree which mimics the look of a tree growing in the wild. Not pruning the bonsai tree goes against this principle.
Also, don’t assume that because you’ve bought an old mature bonsai, it won’t require pruning. It is necessary to prune bonsai trees throughout their lives.
Following are some of the things which may happen when the bonsai tree is not pruned in time (or not at all pruned):
- The tree will look ugly. Pruning (along with wiring) is the fundamental technique of creating a well structured bonsai tree. It is an absolute necessity which will help you in making a miniature tree which adheres to the rules of bonsai.
- As the outer foliage of the bonsai tree is not pruned, the inner foliage will not be able to receive sunlight. This will result in die-back of inner leaves, twigs and branches.
- Also, the inner sections of the tree are more prone to bonsai pest and diseases due to lack of ventilation.
- Furthermore, the dead and decayed parts of the bonsai tree will remain on the tree, adversely affecting its health. Read how to keep your bonsai disease free to know about all the best practices of keeping your bonsai healthy.
- The tree will grow bigger as without pruning there is no way of controlling the size of the bonsai tree. When it grows too large for its container, it loses its desired shape and bonsai style.
- Pruning also involves root pruning. A bonsai tree not root pruned will become pot bound, resulting in the decline of the health of the bonsai tree. Read more about root pruning in pruning bonsai and repotting bonsai sections.
- Continuous decline in the health of bonsai tree due to lack of pruning will certainly result in reduced lifespan or even death of the bonsai tree.
