This is a three-part series on the art of constraint in bonsai. Part 2 is here, and part 3 is here.

A question of scale.

As trees grow, they gradually scale up. The tiny sapling eventually becomes the mighty oak. This isn’t anything you have to do, nature does the work for you.

Ancient Live Oak just south of College Station, Texas

But here’s where it gets fun. Most, if not all, trees and shrubs have an interesting feature built into their DNA. If they have limited space and/or resources in which to thrive, they are often able to adapt and run at a scale that accommodates the available space and resources.

Bonsai takes great advantage of this amazing capability.



Bonsai Artist Walter Pall standing next to one of his magnificent trident maples

We constrain the tree in order to create a particular effect, that of a miniature tree. Those constraints cause the tree to literally grow at a smaller scale and allow us to artfully develop it over time. But it’s not something we do all at once. It’s a series of constraints, sometimes small, sometimes large, applied over many years, along with ample periods of growth in between, that yields a beautiful bonsai.

The effects of growth and constraint.

Some of the best bonsai in the world came from a location in nature where constraints occurred naturally, and the tree gradually dwarfed itself over time. These are collected trees, which we call yamadori. But once collected, we continue to develop the tree by continuing to creatively apply constraints, and by continually balancing between growth and reduction.

Progression from yamadori to finished bonsai. This is one of Tony Tickle’s well known trees.

Old trees in nature have overcome much adversity over the years, and the story of that adversity is told through the trunk, the branches and the roots. Each year the tree tries to grow and adapt within the constraints of it’s current environment, and each year nature throws it some curve balls. By creatively applying constraints, we can simulate some of those curve balls and simulate the effects of age.

Also, on the topic of age: the actual age of the tree generally doesn’t matter so much, it’s the appearance of age that matters. Vendors often will add an age to the sales tag of a tiny tree, and those numbers are often wildly inaccurate. Don’t pay a premium for something just because someone says it’s old. It has to look old.

A tree is a system

When managed well, a bonsai tree is a carefully balanced system of roots and branches. The better you understand this system, the more effectively you will be able to work within it’s constraints to optimize your results.

First, and most important, every tree must grow or die, and allowing trees to grow increases their strength. This is a critical lesson for people just starting out. Pruning a tree weakens it. If you hard prune your tree every single year, or continuously prune it throughout the year, you weaken it over time, and if you then have a bit of bad luck (harsh winter, pest infestation, etc), it can tip the tree into a death spiral. So when we apply constraints, we typically need a period of strong growth to balance things out and keep the tree healthy.

Each leaf or needle that grows in is a little solar panel, and the trees put these out not for our amusement, but for their own survival. Left to their own devices, trees will generally try to keep getting bigger to the extent that they have resources available and room to stretch out.

A lot of the work happens where you can’t see it, under the soil. For this reason, it is critical that you maintain a strong, healthy root system. Whenever I get new trees, I usually just maintain them for that season, but the very next spring I will check out the roots and do any work I need to in order to set them up well for the next few years after that. Good roots lay the foundation for good bonsai development.

The cycle of growth

Buds extend in the spring to generate leaves and small branches. Those branches extend and thicken, and in turn, thicken the branches that they are growing on. All of this ultimately adds wood to the tree each year, and is how a tree acquires it’s rings.

Spring growth emerging from a maple

More branches == more space for leaves to grow == more solar panels == more energy for growth == more growth == bigger tree. Lather, rinse, repeat. This is obviously very high level, but this is the gist of how it works.

This cycle never ends for the entire life of the tree. Even when we keep a tree in a pot, it still follows this cycle, it just has to adapt to the space we’ve given it.

The constraints that we apply to the tree “hack” this process to yield the specific results that we want. We need to prune to maintain the scale we are looking for. The tree doesn’t know that it’s meant to be a miniature now, and it will develop full scale branches if you leave it alone for too long.

Pruning a bonsai. Photo from bonsaiempire.com.

But like I said above, you can’t just do anything. Prune too much at the wrong time and you can kill the tree. Prune repeatedly throughout a growing season to keep the tree looking perfect, and you can significantly weaken the tree. Most of my trees look a bit messy for most of the year. That’s because I let them grow most of the time, and only prune when I have a specific reason to.

Understanding how to work within the constraints that the tree itself presents, while applying your own constraints to the tree each season, is part of the collaborative effort between you and the tree.

Check out part two, where we discuss some common constraints that we apply when developing bonsai.