If anyone has had a chance to look at the Tanaka presentation from January 29, you probably saw this slide , meant to show what terrible things can happen to trees when they are planted next to overhead wiring. (Personally, I didn’t need to be scared into “getting it”; I’ve seen the V-cut carnage in person, as I’m sure have you. There’s a sycamore on Central and Willow that makes me want to weep every time. It’s only one of many victims of severe overpruning.)
To be honest though, I think the slide is a bit of a scare tactic, and I don’t think it tells the whole story. We do badly by our trees for other reasons too. And one of the current recommendations on the Master Tree Plan—a recommendation to plant short trees under utility lines, to avoid the carnage shown on the slide—troubles me just as much, as it can actually result in a different kind of mutilation than what we typically talk about.
So I spent some time yesterday with good old Photoshop, in the hope of sparing myself a thousand words.
The problem with short trees comes from something I heard the tree consultants refer to as “the box”—namely a requirement to have 14-foot clearance of tree branches that overhang the curb, so that fire trucks can have access without hitting anything. This is the red box in the picture.
So what happens when you have a 25-tall tree (that’s maximum height of the trees recommended for where there are wires overhead) and 14-foot “box”? The result is Tree A on the drawing—a lopsided thing, prone to leaning over the sidewalk and losing its branches in strong winds due to its reduced symmetry. I’m sure you’ve seen trees like that; once you start to notice, they are all over the place.
The problem gets even worse if the tree is trimmed to the box while still growing (Tree B). In this case, a major branch gets chopped off sometimes, causing the tree to grow into a P-shape, with no hope of ever straightening up, like a juvenile delinquent from a broken home. Chances are, such tree will not reach ripe old age. Soon, it will be deemed leaning and dangerous, and slated for removal before its time—naturally, at a cost.
One imperfect remedy to correct this is to try and restore symmetry by pruning the other side to match. The result is Tree C, with something like a crew cut that makes it look like it might be OK, if we didn’t know the history behind it. (Or if you prefer, we’ve sent our delinquent to the army to learn discipline to hopefully get him through life without trouble. Yet no one knows what trauma lies behind the young man’s stony expression.) However, the potential of this tree is never fully realized: It was cropped from below (for the box), and often topped from above too, to stay under the 25 ft wire line, if it had taller tendencies. (I’ve drawn that potential in gray on Tree A, just for fun.) It’s a tree alright, but one that provides neither the amount of shade nor the carbon absorption we want it to, and it’s too bare for any birds or other wildlife to nest in. It’s a “sterile” tree.
Now let’s take a look at Tree D. This guy was allowed to develop naturally, while also instructed in the right habits by pruning lightly here and there but carefully, so as not to mutilate or disfigure. The tree has been allowed to outgrow the 25 foot line, but the consequences aren’t as disastrous as some might fear. The part of the tree through which the wire passes is the heavier branches which don’t sway and break easily. Smaller branches have been carefully cleared so as not to catch on the wire, and above the wire line, the tree feels healthy, well-balanced, and fulfilled. It does everything we expect a tree to do, including hosting wildlife, shading, and trapping CO2 and the pollutants that would normally wash down in the ground. It’s a giving tree. It’s the kind of tree we need.
So what’s my point you ask, other than having fun with pictures and analogies? I have two:
1) We need to take a careful look at what in a tree constitutes a danger, and what is a perceived danger. Keeping wires in good order and pruning to remove dead branches is necessary, but what is probably not necessary is to keep certain types of cables and branches from EVER coming in contact with each other, damaging our trees in the process. Scary as the pictures on the presentation slide look, it doesn’t have to be that way. Over-insuring in one department is an obvious detriment to another, and we need to balance the two.
2) We (city staff, pruning contractors, regular people) need to always take into consideration the wholeness of a tree life when deciding how to handle it’s youthful unruliness. Fire truck access is important, and rules are rules of course, but discretion should be exercised when choosing whether to completely “shave” the curb side of a tree, no matter what, or let it develop its structure, so that we can raise trees that last and do well and serve their purpose, not cripples we’ll need to replace in a few years. Doing anything dogmatically, looking only at the present, is likely to be ineffective and costly in the long run.
I was in Walnut Creek yesterday, naturally looking at their trees (left my camera at home though, darn!) and I did not see nearly as much fussiness with trees and wires and clearances as I see in Alameda. Walnut Creek has a great tall tree canopy, yet I’m sure they are held to the same standards for safety as we are. So really, folks, it’s a matter of choice, balance and discretion.
With these lasting words of wisdom, go and do a good job, whatever it is you do, and always consider your long-term impact on the things you come in touch with.