The Botany of Graffiti
A Blackboard Jungle
Not so long ago, my dad, known to his friends and my mother as Wally, brought me to the “old home place” in rural Pennsylvania where he grew up. He showed me where he wrecked his dad’s prized Buick sixty years ago when he was only thirteen; and where he and his friends spent summer days sliding down a steep, slick rock waterfall into a shallow pool that was just deep enough to allow him to emerge from childhood with no permanent spinal damage.
A year or two later, at Boyce Thompson Arboretum near Superior, Arizona, one of their largest red gum Eucalyptus trees was defaced with graffiti by a visiting middle school student—a student who was on the same school tour as the one that I was attending with my daughter. It was more of a mischievous than malicious act, carved into the tree by a kid who was no more destructive than my dad or I was at the same age. This student had quietly slipped behind the trunk of the tree and carved his first name into the smooth white bark with the quill of a feather that had fallen from one of the turkey vultures that roost in these trees every evening from spring through fall.
It was more of a mischievous than malicious act, carved into the tree by a kid who was no more destructive than my dad or I was at the same age.
Had the principal of my daughter’s school (and that of this adolescent narcissist) not been notified the next day by one of the arboretum staff, his inscribed name would have fallen anonymously to the base of the tree in June, July, and August, embedded in one of the hundreds of long strips of bark that are shed by red gum trees every summer.
There is no doubt that these red gum trees present an alluring target. The bark is as smooth as a blackboard and there are half a dozen tempting trees within arm’s reach of this arboretum’s main trail. Scatter a few dozen molted turkey vulture feathers, rocks, and sticks below the trees and you have the ingredients for the devil’s playground.
The good news is that red gums are usually self-erasing because of their own seasonal molting habit, but only if the tool that is used is relatively soft or rounded and doesn’t penetrate too deeply into the bark.
There is an engraving depth, however, where irreversible damage will occur. That point is when a vandal chooses an implement more invasive than a blunt stick or a feather, and rips into the cells that form a thin cylinder around the tree just below the inner bark. These cells are called the vascular cambium.
Cambium cells are sometimes called “tree cell generators” because they are the mother cells that differentiate to creating phloem (inner bark) towards the outside of the tree and xylem (wood) to the inside, as well as other specialized plant cells that a tree wouldn’t want to do without.
There is another layer of growing cells that is located to the outside of the phloem but behind the outer bark called the cork cambium (phellogen). These actively growing cells differentiate to form the outer bark (periderm) of the tree.
From the tree graffiti-est’s point of view, bark can run the gamut from impossible-to-carve, like the deeply furrowed bark of ponderosa pine and cork oak, to the can’t-wait-to-carve smooth bark of quaking aspen, American beech, and red gum Eucalyptus.
Most traditions die hard
I’ve come to realize that, unlike tattooists and plastic surgeons, people that deface trees do not have artistic motives. They are driven by vanity and are mainly interested in reminding the world that they exist, along with the day, month, and year of their existence, and the significant love interest that happens to be existing with them at the time.
In some families, carving a name in a tree is a time-honored father and son tradition. Not only is it validated, but it’s even encouraged by the father, like fishing or spitting. Fish may beg to differ, but of the three, I think tree defacement would benefit from some paternal re-evaluation.
Once a tree seedling has taken root, it is in the spot where it will spend the rest of its life. It has no ability to run from disease or duck out of the weather and it’s incapable of preventing someone from drilling, carving, pruning, or cutting into some part of its anatomy. But that doesn’t mean that it is completely defenseless.
Fighting the good fight
When a tree is wounded, it doesn’t repair the damaged part. Rather, it goes into damage control mode and attempts to isolate the spread of decay. If the tree is healthy and all goes well, the decay will be boxed in or “compartmentalized” and denied the satisfaction of weakening or even killing the tree.
When the bark and cambium is damaged by a tree vandal’s tool, the tree reacts by making new cells around the wound. The cells contain substances called suberin and lignin which make the cell walls impermeable and together, form a barrier to disease. These cells set the stage for the formation of new bark cells (that also contain suberin and lignin) that further reinforce disease resistance. However, the original scar, where the actual damage to the cambium took place, will remain with the tree for the rest of its life.
If carved too deep, the graffitist's scar will remain with the tree for the rest of its life.
There are a few exceptions to this, and luckily the red gum Eucalyptus is one of them. It “refreshes” itself every summer, shedding long strips of sinuous bark that can pile several feet deep under each tree and scatter in a radius that is wide as the tree is tall. From the summer solstice through August, the audible crunch of cast-off bark can be heard under every walking shoe or hiking boot that passes underneath. The drawback is that the baby-soft new bark that is now exposed is particularly vulnerable to a school age vandal’s motivations—saved by the bell, so to speak, by summer vacation.
Boys will be boys
As my dad and I walked along the creek that flowed downstream from the waterfall of his youth in Pennsylvania, I noticed a giant beech tree, easily thirty-six inches in diameter, along the path. Across the face of its uniform, gray bark, in six inch capitol letters, was the heavily calloused but clearly readable remains of the letters: “W-A-L-L-Y.”
I turned and looked him straight in the eyes and asked him if the WALLY that had carved into this tree was the same WALLY that was now averting my glance.
“I honestly don’t remember,” he said. “Maybe. It was a long time ago.”
I let it drop at that. The tree appeared healthy and none the worse for wear. And to my recollection, my dad had never encouraged me to carve into a tree when I was young and naïve enough to do it. My only beef was that he hadn’t shown me that waterfall thirty years ago, when I was dumb enough to take the plunge.