Aesthetics is the study of beauty, form and the correct placement of objects. To the uninformed person, the practice of pruning trees relies on an idea of beauty that has very little relevance to a tree’s health and longevity. By the way, “idea” is a word that comes from the root word “ideal.” Trees are supposed to be perfect. Supposed to be. Many people hold images in their minds of perfection, the balanced tree, that is seldom found in nature.
Trees have made it on earth for upward of 500 million years. That’s an “ideal” any species might envy. I, for one, want to take a leaf from their book.
In the landscape, trees are dying in just a few decades. The lives of trees are shorter in an urban environment than a forest. In a forest, the same species can live for hundreds of years. But what about rural areas? The suburbs and exurbs? Where people live is the environment most arborists work in.
My theory is that, when we take the cycle of nutrients away from trees, we take some of their immunity, not just their nutrient base. Just as a healthy human biome can be washed away by washing – or washing too frequently – with harsh detergents, a healthy tree biome can disappear with too much raking and blower action. I believe that some of the drought stresses we see in California would be reduced by simply leaving cuttings and fallen tree parts on the ground.
I recall the advent of the leaf blower. It was this magnificent tool that was only used at the last part of a job, after raking. Sometimes one guy would be sweeping, then another blowing behind him. Those days are gone. Now, many landscape crews are blowing leaves and debris almost the entire time they are on site doing maintenance. I get it, but I feel we are paying a high price for labor saved. We are suspending particulate matter that humans and animals will breathe, and we are taking that matter, that “litter,” from the bases of plants and trees that could use it.
Dr. Alex Shigo used to call trees and their surroundings “associates.” It’s a useful model for understanding trees and soils, plants nearby and mycorrhizae, which is great for trees because it latches on and happens to exude a waste product the tree can use. I wonder how an associate like that would hang on with a 200 mph wind trying to blow it away? That’s about what a commercial blower is capable of. Don’t get me wrong. I have owned and may again own a blower. I advocate for responsible use, which really means less use.
Unfortunately, many people have an aesthetic sense that drives them to want to clean up areas around trees. However, mulched areas have been appearing more in the landscape, and that helps tree roots in at least a dozen quantifiable ways, such as creation of bug habitat. Infiltration of excess water is slowed, and evaporation lessened. Mycorrhizal colonies are encouraged, especially with inoculation. There is less compaction from shoe, tire and paw. Nutrients leach from mulch to soil (if it is organic mulch). It attracts birds and wildlife and provides soil cooling in summer and soil warming and heat-loss mitigation in winter. No need for weed whippers and the subsequent associated decline or necrosis at the trunk’s base.
In 1993, I worked at Honolulu Botanical Gardens. At that time, the public was criticizing our director’s insistence on mulched areas around nearly every tree. The trees had always been integrated into grassy lawn areas or dirt areas. Mulches were changing the aesthetic impact of this garden. This had people up in arms at meetings. Now, in 2019, mulch is a common sight there. Mulch has been applied correctly and incorrectly for at least 20 years, and thus the aesthetic sense has changed for people growing up around it. (There is now the phenomenon of too much mulch. Arborists joke about amateur landscapers who practice “mulching to the first limb.”) It is a good thing that mulching is common. But it is not a good thing that mulching is poorly understood. Subtleties of our profession need to be shared as never before, because those who make the decisions and pay our bills need the education.
But what about pruning? We lift limbs without question for two main reasons – and one lesser reason:
• Hazardous nuisance. If a child or adolescent cannot climb the tree by reaching the first limb, he or she cannot fall from it. If he or she falls from it, the “owners” of the child sue the owners of the tree. (Sound ridiculous? Ask yourself, if we cannot own a child, does it not follow that we cannot own a tree? The Native Americans have had a lot to say about this, and I need not get on a soapbox to preach to the choir.) Low limbs are commonly removed for this reason.
• Low limbs, coincidentally, are shed first. Thus, the responsible pruner often removes them to beat the trees to the punch. No lowest, oldest limb, no accident. If it is carefully considered, I haven’t got a problem with this. But a cookie-cutter approach is used by many tree services, and one can tell their work at a glance by the absence of low limbs coupled with the lack of intelligent pruning higher up. One is tempted to draw an analogy to the business model of these services, where turnover is high and there is no room at the top for light to shine through.
• Lastly, limbs are often removed for the clear passage of pedestrian and bicycle traffic, and that of trucks and cars. Many municipalities have a rule for sidewalk or parking-strip trees. I do think those are smart. Normally, they are eight feet above sidewalks, 12 or 13 feet above roadways. I have often taken off a low limb for a customer to free a path from the inevitable droop of the lengthening limb. But when we question the drooping limb on private property, we can see these do not always need to be done. In botanical gardens, limbs are often propped and pruned on older trees so we can feel the bark, so different than that of the trunk, or we can pick a leaf or take a selfie.
In a private yard, a homeowner may want his or her kids to climb trees. When my kids were young, they spent hours a day aloft in the maples out front. Fallen limbs under trees can be habitat and erosion control. Must we always see this as a mess? Leaves and litter such as fallen fruit are food for the arthropods, insects, worms and various critters who are associates of the tree. Why not encourage them?
Doesn’t it seem that the trend in aesthetics for trees should be tempered with informal natural play spaces? At least from an arborist’s perspective, it does.
Traffic can be rerouted around trees in some cases. Low limbs also provide excellent screening of views and/or windows.
I’m not advocating for these practices. I am advocating for questioning some of our assumptions.
Jack O’Shea is a Certified Arborist living and working in Oroville, California.