Pruning is a necessary step in the creation of a bonsai. The idea of letting loose on a delicate looking tree with a pair of pruning shears might be scary but it is one of those things that gets easier with time. The more you do it, the more comfortable it becomes and can actually become an enjoyable experience. (I find this to be true with most things in the art of bonsai)
Pruning is basically removing parts of the tree that does not serve it in its quest to be the perfect bonsai. Pruning can be done on the roots, branches, leaves and buds.
There are 2 types of pruning
- Maintence pruning
like the name suggests, maintenance pruning is done to maintain the shape and size of the tree. It is done regularly to remove dead or damaged branches leaves, flowers and fruit. Removing any parts of the tree that drains its energy will encourage new and healthy growth. Maintenance pruning also allows sunlight to reach to the inner branches and leaves.
Can be done throughout the year
Is a more hard core type of pruning that can include removal of primary branches. It is mostly done when the tree is still young to manipulate it into one of the styles of bonsai. Should be done only when the tree is in dormancy since it will cause a lot of stress on the tree.
What parts of the tree can be pruned?
- Shoots and leaves
Why we have to prune bonsai
There are many reasons why we need to prune Bonsai Trees.
- Removing dead or damaged branches and shoots prevents disease, pests and rot from infecting the tree.
- Regular pruning keeps the tree looking neat and maintain its shape
- To get rid of protruding branches or those not growing in the right direction.
- Pruning encourages new and healthy growth (removing weak shoots can encourage rapid growth in the tree)
- It can also be used to restrict growth for example leaf pruning can be used to reduce the leaf sizes.
- Increase access to sunlight and fresh air for the whole tree. Pruning outer edges of the tree allows sunlight to reach inner shoots.
- Pruning can be used to obtain balance between the trunk and roots of the tree.
- Removing wilted flowers and fruits improves development
Effects of over pruning
Some trees will find it hard to recover if they are pruned too much. On the other hand, a tree that is never pruned will continue to grow like a normal tree and will outgrow its pot.
Also known as defoliation is a part of the regular maintenance done when taking care of a bonsai tree. Removing leaves from the tree serves several purposes.
For trees with unhealthy leaves, for example where leaves have turned brown, are rotting, are infected with a disease or otherwise damaged, pruning can play an integral part in getting the tree healthy again.
Leaves and foliage that have outgrown/are protruding are removed to maintain style and shape of the tree.
Leaf pruning can also be done to make the tree more compact through ramification which is done to ensure that a tree has branches of varying thickness so that that the twigs at the end are finer than twigs on the rest of the tree.
Difference between pruning and pinching
Pruning conifer leaves is usually done by hand through a method called pinching. This is because when pruning conifers, cutting the tip of a leaf will make the rest of a leaf go brown.
Pinching is very easy to do. Hold the tip of the shoot you want to pinch out between the thumb and forefinger to pick out the tip of new shoot. Removal of the tip will make the tree to bud lower than it normally would.
There is some debate whether pinching should be used on Junipers. Many experienced growers will argue for or against the practice. I came across this interesting article written by Michael Hagedorn, an experienced bonsai artist who says that junipers should never be pinched. Here is a link to the article on his website.
When to prune leaves: General pruning like removing dry/damaged leaves /shaping new growth can be done throughout the year.
How to prune leaves
Leaves can be trimmed using pruning shears/scissors; by cutting the leaf off from its stalk. How much you prune will depend on the specie of tree and style you are going for but for most species it is recommended to remove 2 leaves for every 6 to 8 leaves on the tree.
Changing the direction that a branch is growing can be achieved by removing most of the leaves from the branch and leaving a bud that is growing in the direction that you want the branch to face/grow. This technique can only be done on larger branches or shoots that have several internodes. Any new growth will be in the direction of the remaining bud.
- Pruning branches
Pruning branches allows the inner sections of the tree to have access to sunlight and fresh air.It can also be done to reduce the size of the trees leaves so that they are proportionate to the size of the tree. Pruning can also be done to change the direction that a branch is growing.
How to prune branches
Branches can be pruned using concave cutters which are bonsai tools which are shaped so as to allow the wound to heal quickly.
Pruning scars/ wounds
when a branch is pruned, the wound left behind will heal into a scar on the branch or trunk of tree depending on where the cut was made. To aid quick healing and to avoid ugly scars, some people recommend using a cut paste on the wound.
- Root pruning
Root pruning is done to control the growth of the roots and also to control the size of the tree. Further still, when roots are pruned, each of the pruned roots develops smaller/finer roots which make absorbing nutrients from the soil easier.
A tree whose roots are not trimmed will become root bound. A root bound tree is one which grows so many roots that fill the bottom of the pot that there is no space for new root growth. Sometimes the new root growth is so much that the pressure from the roots growth will push the tree from the pot. Root bound plants do not absorb as much of the fertilizer from the soil resulting in the plant becoming weak and slower growth than is normal for a miniature tree.
How to tell if a tree is root bound
A root bound tree develops very slowly and can even develop chlorosis.
Sometimes roots can start to grow out of the drainage holes on the pot.
When to prune
Late fall and early spring for temperate climates is the perfect time to prune roots.
Root trimming instructions
- Remove the tree from the pot; if wires were used to hold the tree on the pot these should be cut with a wire cutter.
- To remove the tree from the soil, you can cut into the soil using a saw but care should be taken not to cut too deep into the soil as this can cut roots
- A root hook can be used to cox the roots out of the pot. For a smaller tree, chopsticks can be used instead.
- Trim tap roots back – For bonsai the goal is to avoid a dominant root but a root system made of fine and shallow roots
- Trim back the smaller roots using root scissors.
- When repotting, the tree can be placed in a new pot if it has outgrown its pot. Repotting is also an excellent time to change the soil mix.
- Once the tree is planted, it should be watered thoroughly
How often roots should be pruned
This depends on the size of container tree is potted in, what species it is and the environment under which it is grown.
Tips on root pruning
- Should not be done on unhealthy plants unless pruning is necessary for example when the tree is unhealthy due to root rot. Even then only the rotting roots should be removed.
- Should be done at the end of a trees dormant period before its growth period.
Repotting a dying tree
Repotting can be done to try to revive a dying tree. Although it does not always work, it can be tried as a last resort to try and get the tree to start growing again. Follow the instructions above. Sometimes stressed trees can be planted in the ground like a normal tree until they are healthy again, and then repotted.
photo credit: Shipher Wu