Pikes/Pines | Scarred, stunted, smothered, and peed on — Capitol Hill’s street trees are hardcore

Be nice to trees. Don’t staple stuff to them. (Image: Brendan McGarry)

Every once in a while I like to take a whole day and just walk around Seattle. I’ll wander about admiring plantings, architecture, and all the beautiful variety cities have to hold. Usually I find myself being surprised by the birds I find in the busiest blocks and realize I forgot about a specific tree planting. Seattle, and Capitol Hill truly are beautiful places worth admiring in the style of a slow poke, poking about.

This most recent meander, I had trees on my mind. Despite Seattle’s urban canopy loss, (the most recent data shows a loss of about 255 acres of trees between 2016 and 2021) the Hill and Seattle in general are home to some beautiful trees, both planted purposefully or growing wild.

However, while Seattle aims to increase tree cover by 30% by 2037, I can’t help but wonder what it looks like for the trees once they’ve been planted.

As an arborist and lifelong gardener, I already knew it was hard being a street tree. But I was confronted by some horrible examples on my walk. Once a tree is planted and manages to survive into maturity, it still has to contend with a host of trials. A tree in the wild has to deal with wounds, disease, weather events, and more. But our urban street trees have even more piled on. They are stuck between sidewalks, power lines, and roadbeds. They are mismanaged and mangled. A cherry I saw on Harvard between Pike and Pine had been hit by cars, mangled by bad pruning, tagged, and even lit on fire. Frankly, it’s astonishing that we have any trees alive and lining urban blocks at all.

The cherry tree mentioned, living a particularly bruised life. (Image: Brendan McGarry)

Arborists, landscape architects, and other folks in charge of planning and implementation do their best to get trees off to a good start and the very first step is putting the right plant in the right place. Embarrassingly, I once wrote a Pikes/Pines mentioning how I thought we should have more native trees as street trees.

While in an ideal world, I wish this were true, the reality is that urban soils, hydrology, and stresses are too much for many PNW native trees to handle plus many of them just get too big (there are notable exceptions like Cascara and Vine Maple).

Street trees need to be the right size at maturity, be able to handle the restricted root space of a parking strip, and be ok with the usually poor soil said spaces hold (here’s a good rundown of what to think about). Not all the mature street trees across Seattle are great choices today because for quite some time it was a free for all and people planted whatever they wanted. Now you need a permit, which I think is a good thing, because it both educates people and stops poor choices from being made which results in mangled trees at best, dead ones at worst.

Despite good intentions, some street trees don’t get off to the best start because they aren’t properly planted or cared for from the beginning. As I walked from Lower Queen Anne through South Lake Union and up to the Hill I saw countless trees either planted too high or too low – so far as I could tell they were all surviving, but improper planting can cause issues down the line and lead to premature death of a tree. Too low and roots can be suffocated by standing water, the trunk can get girdled by its own roots, and excess moisture collecting in the shallow can promote root rot. Too high and the root ball can dry out, become stunted, and unstable. Poorly planted trees are not intentional negligence of course, they are just what happens in a big city with lots of stuff going on – it’s pretty hard to make sure everyone is on the same page, even with municipal oversight.

A decently planted tree; a replacement for a declining tree on the South end of Cal Anderson. (Image: Brendan McGarry)

Seattle’s tree code may exist to make sure trees receive more protections and better care, but that doesn’t always mean the people who interact with trees everyday know how to manage them, care to learn, or even consider the codes when they do something. This is most apparent when I admire the pruning of rushed property managers, poorly trained landscapers, random passers by who are bothered by a specific twig, and that guy who backed a box truck up into a branch and broke it off while I was daydreaming about writing this article. The resulting wounds – torn bark, cuts into the trunk and branch collar, and stubbed off branches are scars trees bare for life. The most egregious wounds for street trees are often from being struck by vehicles because they can be large, ragged, and difficult for the tree to seal up.

When we cut through the outer layers of a tree (bark and subsequent layers below), even if done properly, we are creating a wound. If this is done in a good place, like just outside the branch collar, the tree has a pretty good time of sealing up the spot with wound wood, a reactionary growth that physically inhibits access to the cut (trees also have chemical reactions explained by the CODIT Model, or Compartmentalization of Decay in Trees). When a wound cleaves through bark on the trunk, a branch flush cut, or a tear rips through a branch collar, trees have a harder time sealing up and this leaves them more susceptible to things like fungal infections and invading insects.

An example of poor pruning. Really poor. (Image: Brendan McGarry)

While a tree is trying to manage a barrage of wounds, it also has to contend with below ground pressures. Impacts on roots are easily overlooked or not even considered by most of us. Grade changes that suffocate or expose roots can be devastating to even a mature, healthy tree, as can the severe and often improper root “pruning” that can happen during construction or maintenance of underground utilities. Even trees in a park that simply have heavy foot traffic around their trunk can decline over time because compaction is another serious threat. Both ethically and legally, construction project managers and arborists should work to minimize compaction around the roots of existing trees by creating tree protection zones that restrict access to the critical root zone of a tree. In practice this probably isn’t done as well as it could be because of all the moving pieces that go into new construction or major renovations – without enough people to enforce such standards, tree protection falls down the list of priorities.

Tree protections aside, the soil that most street trees root into is far from an ideal medium. When we build cities we tend to make a mess of the organic layers of the soil. Sitting nearer the surface, these layers are full of good nutrients and beneficial bacteria and fungi. What usually gets left is backfill from digging out foundations or material trucked in from elsewhere. It’s frequently lacking in the essential nutrients plants need, which is why compost and wood chips usually accompany new plantings and mature tree amendments. You can probably imagine what good, healthy soil looks like versus the rocky, loamy stuff that fills the majority of parking strips.

Basal sprouts, a signal this tree isn’t happy. Not only is it squeezed into a small space but its roots can’t breathe with the fake turf over what little soil is there. Plus, I imagine it gets peed on a lot. (Image: Brendan McGarry)

While this might seem like a non sequitur: Seattle has a lot of dogs, around 160,000 in fact. During my walk I saw more dogs than children. Granted it was a weekday, but this is still reflective of the fact that Seattle has the highest number of married couples with a dog or a cat, and no kids (13% of the total population according to research in 2024). Most of those dogs go on frequent walks and frequently urinate, often on trees. It might seem innocent that dogs mark and remark on landscaping, but over time that urine builds up excess nitrogen, which is difficult for plants to deal with and can lead to poor growth and even root burn. Pee is also salty, and excess salts in the soil mess with a plant’s ability to take up water, dehydrating them. Now, I don’t know that there’s any tree I can go find that’s dying because of dog pee, but I do know that in this already stressful world, getting peed on frequently doesn’t help (unless you are into that, I’m not here to kink shame).

There’s a strong chance that in this moment you didn’t need a reminder that even right here on your block things are pretty hard. But my hope is that also you see the incredible resilience of street trees and understand that when they are properly chosen for a specific site and cared for, they can still thrive.

After all, even in the best of conditions, trees have to live with wounds, invasions from pathogens, and environmental changes. If you want to have healthy trees (and other plants – tree folks can forget there’s entire ecosystems that trees are just members of), it should be empowering to know that you can have a direct impact on their health. We need trees, particularly in the most densely impervious of places to help make our cities more liveable, healthier, more beautiful, and even to help deal with stormwater and cool our homes.

You can advocate for and even directly care for local trees. Join a group like Plant Amnesty and learn to properly prune. Participate in the Trees for Neighborhoods program or volunteer with Trees for Seattle. And maybe don’t let your dog pee on a tree over and over again.

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