root pruning

Deciduous Tree Development

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After last month’s presentation on developing deciduous bonsai, I thought it would be great to review some points and amplify others. While reflecting after the meeting, I realized what I was providing was a very wide overview of the process, but it was akin to talking about Junipers, Pines, and Spruces all at once. There is a lot of variety and nuances to deciduous trees that we were not permitted to even touch on, so I wanted to mention some other great sources of information that you might want to review to expand on the concepts that we talked about. 

First off, there is the article from this column called Bonsai From the Ground Up, where I talk about some of my experience with field growing trees in the backyard. You can find it on the BSOP website under Resources; Scott’s Branch Tips. There are also two programs on Ryan Neil’s Asymmetry pod casts, via Mirai Bonsai. On one, Ryan talks deciduous development with none other than our own Dennis Vojtilla, and on the other he talks with Chris Kirk and Gary Wood on field growing techniques and strategies. They make great listening while working on your trees. 

We started our conversation last meeting with the acknowledgment that you can’t just go collect a great deciduous tree, like you might a conifer, or run to your local shop and expect to find really great material. The most dependable method is to simply grow them yourself. It follows then, that the earlier you start in a tree’s life, the more success you will have. Nothing beats the movement that you can put into your trees when you start with seedlings or rooted cuttings. That initial movement is so important. No matter the tree species, conifer or deciduous, I never allow a tree to grow straight out of the soil. It always emerges at an angle. And that means that I am already working on the root structure that is so critical for deciduous trees. 

It definitely means some root pruning and if there is a tap root, or an overly strong root of any kind, this is the best time to give it its walking papers. It’s gotta go or the whole tree suffers. So be ruthless. Better to make a hard cut now, than to set the tree back after ten years of hard work. Grow the tree in a pot for a couple of years to get that movement and root based established before moving it to the ground. If it grows too fast, at least it grew with great curves. 

Straight trunks, no matter what size, don’t really have a place in my garden. When you make curves, think of the size of tree that you want to make. A large tree requires larger curves. A shohin tree may only move an inch or two to one side or the other while a larger tree might shift almost a foot in any one direction. Don’t forget to make it move in three dimensions – front to back as well as sided to side. Also, wire well beyond what you think you will want. The extra length will actually help you bend the sections you desire and provide you with a bit of cushion for shape. You never know for sure how a tree will develop. You can make the decision of where to cut it next season. 

When you are ready to enter the next stage of development, you can move up to a larger pot, place the tree in a wooden box, or plant it in the ground. Things grow many times faster in the ground, but that is not always helpful. If you want a large, bulky, masculine trunk, it will really help. However, it is much more difficult to manage that growth while it’s in the ground. If you want a more delicate, feminine line, it may be better to employ a wooden box or larger pot that you can watch on the bench. Boxes are an underutilized tool, especially by me.

You can also use them to rejuvenate a lagging tree. 

So now that your tree is well on it’s way and things are growing along and the trunk is getting the proportions you desire, it may be time to make a big cut and redirect the growth in a new direction. This of course does two things – it builds good taper into the design as well as introduces more movement. The tricky part here is to not slow the tree down. That’s why I never prune heavily until I have a branch of sufficient diameter to take over the sap flow where the cut is. This can be very subjective, but as a rule of thumb we might say that it needs to be at least 20% of the size of the main trunk. If it’s not, then let it grow some more. 

And never rely on just a bud. They can easily wither away and then you are back to square one. The main point here is to not cut right where you want it to end, but rather at least one trunk diameter above the new leader branch. This will allow the tree to compartmentalize the wound. The following year you can reduce it either to where you want, or to where the tree has died back. This is a much, much safer technique and leads to complete healing of scars and predictable results. Do this process as many times as you need until you have your desired results.

You may have a tree in the ground from 3-10 years, so you will have plenty of time to practice. I used worked on my trees in the ground twice a year in order to get what I wanted. 

Be sure to keep working on the roots. I like to prune roots every other year. This allows the tree to really gain some strength from growing in the ground but limits certain roots from growing too fast and sapping strength from the others. We are looking for balance. That way, when we pull it out of the ground or a wooden box, we can move it right into a bonsai container. Happy growing!

Scott Elser