The Bonsai Paradox: How Do We Keep Trees Small?

One of the most frequent questions that we receive from people unfamiliar with bonsai (after the question: “how do you keep them alive?”) is “how do you keep them so small?” The general public seems convinced that our wee trees are Lilliputian freaks that have been coerced through starvation and bondage. Maybe yes, maybe no, but before we address the question of how to keep a bonsai small, it is helpful to first ponder the question of what bonsai is.

Bonsai is the artistic cultivation of miniature trees in containers - grown and styled to defy time, gravity and perspective. Bonsai is really just an illusion that inhabits the intersection of science, art and horticulture. It is an illusion in the sense that the bonsai artist attempts to convince the viewer that the tree is something that it is not. It has been said that bonsai is a paradox: trees are manipulated to make young look old, to make tall look short, to make large look small, to make healthy look tortured and to make otherwise sensible trees appear to defy gravity.

You have seen proportion diagrams of the human body. If pictures of a new baby, a growing child and an adult are all proportioned so that they are the same height, and set next to one another, the head of the baby is much larger in comparison with that of the child or adult. The head of a baby may constitute up to 1/3 to 1/4 of the total length. In an adult, this fraction falls to 1/5 to 1/6. It is this relationship that makes each stage in development so immediately recognizable.

The same is true with trees. Young trees grow long and thin as they stretch to reach above the canopy to the sun. There are fewer branches, and the distance between branches is greater (relatively of course). The ratio between the width of trunk and width of branch is small. Old trees, on the other hand, have remarkable taper. They have thick, expressive trunks that progressively thin through smaller and smaller branches until they explode outwards in a spray of fine branchlets with leaves. Old trees have thick, well-developed roots that often protrude above the ground, and the trees themselves are often gnarled and seemingly tortured by exposure to the elements. If you take a picture of a young tree and a very old tree and scale them to the same size, they look very different, with recognizable differences in trunk girth, shape of the crown, and density of fine branching.

So, back to the original question: “How do you keep bonsai small?” The simple and obvious answer is that you trim them aggressively. You cut the branches back to reduce the distance between branches and to encourage taper and fine growth, and to CREATE THE ILLUSION OF A LARGE, OLD TREE. You trim the roots to encourage a fine, dense, healthy root mass with a higher proportion of root hairs to woody roots. By cutting back the top and the bottom, you allow the trunk in the middle to continue to grow and develop, enhancing taper in both directions. By reducing the root mass, you are able to place the trees in ridiculously small pots, further creating the illusion of size and age, and causing the tree to appear to defy gravity. (Although as we know, it is actually wired into the pot to keep it from falling over.)

However, the other, more complicated part of the answer involves nature vs. nurture. By forcing the tree to deal with limiting conditions, the tree learns to develop new ways of coping: growing smaller leaves, reconstituting its root mass, throwing out new branches where none existed before, adapting to new nutrient supplies. In essence, we convince the tree that it can make a better living as a small tree rather than a large one. In so doing, we create large, old trees out of little, much younger ones, and we keep our old trees small.

So next time someone asks you how you keep your bonsais so small, look thoughtful and reply: “I don’t keep my bonsais small. They do it themselves.” Then smile and change the subject.

Let’s keep the illusion and the paradox intact.

A Green (And Red) Thumb For Christmas

What then, exactly, is a green thumb?

Why is it that some people on this planet are able to endlessly surround themselves with lush, thriving plants that seem to grow themselves, while others couldn’t keep a cactus alive if their own life depended on it?

Those who can’t, attribute this strange power to something mysteriously referred to as a “green thumb”. But those who can, know better.

There is nothing mysterious about a green thumb. It’s not like trying to hit a round baseball with a round bat, interpretting tax law, or solving quadratic equations. It’s not a secret skill passed down from teacher to student since antiquity by covert growing societies, and it’s not a special “gift” bestowed by Mother Nature.

A green thumb is really just simple empathy. It is the ability to sense what a plant needs and to provide it - when the plant needs it. More importantly however, it’s the ability to just stand back and stay out of the plant’s way. In the end, it may be that last part that is the most important.

Plants are marvelous evolutionary inventions. They, and they alone, have discovered a way to harness the naked energy of the sun and to package that energy into little parcels that can be used in a myriad of ways. Plants are able to take the most basic of substances – water, carbon dioxide and what nutrients they can scrape from the soil – and produce structures and substances of the most amazing complexity.

Back before we began to put plants in containers, they grew in the ground. They tied their tap roots into the soil and then sent the other roots off in search of food and water. They raised their tops towards the sun, the source of it all, in spirited competition with other plants for the best position. They discovered, through trial and error, what to avoid and what to seek out. They learned to move away from gravity and towards the light. They learned to trust the climate and to avoid the weather. They learned how to continue to grow, regardless of the damage, change or misfortune that was passed their way.

As some wise old fart once said: “If you take a tree from the environment and put it in a pot – you owe that tree!” Here’s hoping that your happy plants are giving you a green and red “thumbs up” this Holiday season.

Chlorophyll's Retreat

Autumn. The weather may not know what time of year it is, but the trees surely do. Even a huge sugar maple, lounging quietly at the edge of the woods overlooking dry, beaten-down fields, is exhausted. Its leaves are dull and worn, riddled with the wounds of insect wars, mottled with faded yellows and edged with the brown of rot and desiccation. For this old maple there is no more growing to be done this year, not above ground at least.

The trees, the deciduous ones at least, know that it is time to begin to invest their gains, cut their losses and close up shop for the winter. Deciduous trees are like Europeans. Each year, they take an extended vacation at the most advantageous time of the year. It’s part of their nature, their heritage. They use the time to assess, regroup and renew themselves. Evergreens on the other hand, are more like Americans. Evergreens seek to eke out a living continuously, regardless of conditions, with less concern for such frivolities as taking time off. Figuratively, you would never see an evergreen wearing a tiny Speedo at the beach.

Spring seems such a long time ago. But one perfect night last spring, in response to some mysterious combination of increasing day length, the warming of the soil, and the jump-start of the hormone factory, the trees threw open their buds, and unfolded delicate leaves like the damp new wings of a butterfly. These wafer-thin leaves stretched between strong veins exposing thousands of square feet of tiny chloroplasts jammed with chlorophyll to the sun.

Chlorophyll is a complex and relatively unstable compound that is able to perform miracles with sunlight. But for all of chlorophyll’s complexity, its primary function is simply to use the sun’s energy to split open water molecules. In doing so, a cascading stream of hydrogen ions are liberated that rocket around like bowling balls setting a whole new series of sun-capturing reactions into motion. During the summer, chlorophyll is continuously used and must continuously be replaced. It’s rich green color dominates the lesser yellows, oranges and purples of other pigments. But in the fall, when the tree no longer needs to produce energy, the production of chlorophyll ceases, allowing the leaves to finally sport the dramatic fall colors of carotenes, xanthrophylls and other pigments laid bare by chlorophyll’s retreat.

In the fall, those tender young leaves that once provided precious surface area to capture the sun, now pose a liability, and expose thousands of square feet of surface area to the killing winds of winter. The deciduous tree makes the decision. It will rid itself of the leaves, but only after it withdraws all available energy sources back into its interior, deep into the tissues and roots, where it can be stored until it is needed next spring. To be ready for spring, the tree produces tiny buds that spend the winter exposed, like paupers with blankets pulled tightly around their shoulders. They turn their backs to the wind and the cold and hunker down like a small pack of hobos, huddled around a garbage can fire. They reduce their needs and try to outlast winter – the long, long winter - waiting for the day to again lengthen, the soil to warm, and the hormones to again flow.

And then on a perfect night in the spring, when it can wait no more, the tree relaxes. Stripping the blankets off the shoulders of its buds, it unfurls leaves like tiny flags and makes its charge – running screaming to the sun as naked as the day it was born.

A Dormant Tree Wakes In The Middle Of The Winter

It’s the middle of the night. You awaken with a start to pitch darkness, a little lost and surprised, more than a bit disoriented. You could be anywhere and it could be anytime. You glance at the small clock at your bedside and realize that its only 4:30 a.m. It’s early. You still have a couple of hours until you HAVE to get up. Reoriented and reassured, you pull the covers up to your chin, snuggle deeply back into your spot and resume the refreshing sleep of the recently-back-to-bed.

Dormant plants in the winter can’t be much different. They too are occasionally awakened from deep slumber by a January thaw, or a string of sun-on-your-face warm days that remind all living things that Spring is just around the corner, somewhere. The plant too is disoriented and surprised. Is it time to get up? Is it time to wake up the buds and start pumping sap up from the roots? The plant glances at its bedside clock – the sun – and gages the time until it must arise from dormancy. It’s hardly mid-January. The plant doesn’t have to rise and shine until at least the 2nd week of April. Reoriented and reassured, it hits the snooze alarm and goes back for more rest.

By comparison, a dormant tree stored in a darkened basement or windowless garage as no sense of the time of year other than its own marvelous internal clock. It knows that it certainly must be mid-February but it has no way to verify it. So it lays half-awake, half-asleep, afraid that it will oversleep. The rest it gets is fitful, the final awakening abrupt.

I have no scientific evidence to back this up. It’s just a hunch.