Problems with Municipal Street Tree Code

First off, a slightly late Merry Christmas to all! We hope no one’s grandma got run over by a reindeer this year.

Well with the holidays more or less behind us, I’m certain we must all have our mind on just one thing, which of course is street trees. Is there anything more enchanting than the silhouette of bare winter branches against a dark, rain-soaked sky? Come to think of it, perhaps there is.

I’m going to dive into what I think is wrong with municipal street tree code, and in so doing I’m sure this is going to sound like another one of those really negative posts. Am I just here to pick on municipalities for creating policy on this stuff? If we’re doing things so wrong, then what are my suggestions for positive change? Well, with the publication of this blog post comes my commitment to follow it up with something productive. That may take me a few weeks but we’ll get there.

Let’s start with an example of why I think this is necessary. Coincidentally, Lance Wright recently posted the following commentary, with photos, to Facebook:

“Portland has been planting Parrotia persica frequently as a street tree, probably the cultivar ’Vanessa’. The species is ‘decurrent’, with weak apical dominance, as it has a shrubby form with competing leaders. Often times these tend to sucker and sprout, even without pruning or damage, as does the tree pictured here forming a very congested silhouette down to the ground. These can also be quite broad relative to their height…making them a questionable choice for narrow parking strips such as this. As street trees are rarely pruned /trained this is what you can get. This one has been in place less than five years and is already encroaching into the street and taking over the sidewalk. Some Parrotia are better behaved, but I often see this in SE Portland. I do love these in the right place…I have a 30+ year old one in our garden!”

Photos by Lance Wright

So I’m just putting that out there as an example to introduce the topic. It is apparent that something has gone wrong in this instance, because the result is less than desirable. It is worth exploring what that might be.

Rather than Portland, however, my frame of reference here will be the Street Tree Guide for the City of Port Angeles, since it is the city closest to our nursery that has any kind of street tree code. This document is available online here.  (Parrotia is on their list as well! By the way, if any such document exists for Sequim, it is not online that I can find. Let us hope this means it is not too late to craft a more sensible policy!)

I want to begin by saying that I don’t think there is anything wrong with just having guidelines in general that concern street trees. One has to start somewhere, and something is better than nothing. No city, nor its residents, want street trees to rip up sidewalks, drop heavy cones on cars, or otherwise become a public hazard. I can also say this policy is not in any way consistently enforced, as one can tell just by looking around the city. Whether we think a high level of enforcement is good or bad, I would put forth that a city should have the goal of drawing up a plan that allows for easy and consistent enforcement with a minimum of ambiguity or exceptions. That way no one feels like they are being treated unfairly.

Unfortunately, however, a quick look at this document reveals some inconsistencies, which I will describe. One also finds quite a few errors of spelling, word spacing, underlining and layout that make it look a bit sloppy and unprofessional. I’m not saying I’m always perfect in that regard myself, but it jumps out at me. (I’d be glad to fix that!)

(Click images to enlarge)

I’ll skip over the first page, which I don’t consider to be the most controversial or problematic part of this document. Moving on to the second page, we have a set of guidelines which mostly make good sense and are fine, until we come to the part about minimum caliper requirements. After some consideration I’ve concluded that these requirements are a big part of the problem. Having looked into this topic a bit, I’m wondering if there’s something I’m missing, because the reasons I’ve unearthed so far for establishing minimum caliper requirements just aren’t great. Generally they seem to have more to do with project bids by landscaping firms, rather than individual homeowners: municipalities don’t want landscapers cutting corners on tree size to reduce their costs and appear more competitive. There is also the issue of tree replacement: if a large tree is lost there may be a perceived need to replace it with something immediately substantial. (Even this is debatable, as I hope to demonstrate later.)

The main problem with caliper standards is that they are far too limiting for everyday homeowners or gardeners. The homeowner is going to have a lot more tree options if not restricted to what is available in a large caliper. Also, if they are paying for the trees themselves, this could be the difference between buying a tree vs. not buying it at all, if they are on a tight budget. In my view the homeowner should be automatically exempted from this requirement except perhaps in instances where they are responsible for the loss of a large tree that is being replaced. There are other reasons why cities should be much more open minded about this as well, but I’ll get to that in the follow-up post.

So here we have the list of recommended large and medium trees for Port Angeles. First of all I notice that at least half of these trees are going to be difficult to find in any size. Suppose we classify trees three different ways: those recommended by municipal tree code of Northwest cities, those available in our local nurseries, and those that are actually the best performers in our region. We would have three very different lists, with some overlap, but a lot less than you might think. This discrepancy is unfortunate but there it is. For example, not once ever in my life have I seen Osage Orange in a nursery around here; it is exceptionally rare in the Northwest.

Then I notice that some of the medium trees grow larger than some of the large trees. So that’s interesting. In general some of the heights seem a bit “off” for what may be expected in our climate. But then others are accurate enough. This leads me to think parts of this list were assembled from a city or cities in a different climate, as some trees grow to a smaller or larger ultimate size in our climate than described by many popular references. A good regionally specific reference as to what ultimate sizes for trees we can truly expect in our climate is found in Trees of Seattle, by Arthur Lee Jacobson (2006). The reader will find some major surprises as to how certain tree species (commonly sold, and otherwise) have performed in the Northwest over time. However, even in that book, some gaps exist for species that haven’t been established in our region for very long.

I find it interesting that small trees are not preferable. This may be because they don’t cast as much shade or contribute as much canopy for wildlife habitat or sequestration of pollutants. There may be other reasons I haven’t thought of. I think we ought to regard this principle with a great deal of flexibility, as the homeowner may wish to use the space for something besides grass and one huge tree that shades out everything around it.

In general the selection here doesn’t excite me too much. The first thing I would take off the list of small trees is Prunus virginiana. It is ugly and suckers everywhere: I know this because I have been trying to eliminate it from our property for years. I would also note that Acer davidii (never have I seen this in a large caliper, BTW) certainly looks far better in about half shade than in full sun. Ideally a street tree should be adapted to mostly sunny and relatively dry conditions; species should be selected with this in mind.

So taking those lists together, here are the main things that stand out. I know it’s kind of buried down here, but the following issues are really the central point of this post:

1. All the recommended trees are deciduous.

2. The majority of these trees are native to climates where it rains all summer.

So to the first point, although I don’t automatically hate all deciduous trees, I am an advocate of using broad-leaf evergreens far more than we do around here. Some have been accused of looking “gloomy” in our winters, but for the most part I think they add interest by giving you something to look at in winter besides bare sticks. Many of them have interesting foliage, form, or bark that is very appealing when the winter sun hits it. There are literally hundreds of options for broadleaf evergreen trees that do well in the Northwest; many of which you can read about in books such as Trees for All Seasons. Even if you are not a huge fan of broadleaf evergreens, there can be no sensible reason why ALL the trees on the list need to be deciduous.

But I am sure this all comes back to the caliper requirement. Broadleaf evergreens are generally grown in containers, rather than produced in the field, and are thus seldom available in the large caliper desired. Put another way, because they are container-grown rather than field-grown, they are more expensive to produce to get the same size as a comparable deciduous tree, and thus are not produced because of the lack of demand for the more expensive option. Doubtless this is a major reason they have been largely overlooked.

Now to the second issue. I am aware that some planting areas are irrigated (at least until the irrigation system breaks), and there is a certain amount we can get away with as far as using trees native to climates with more rainfall during the growing season. In the follow-up post I will discuss what I believe makes the most sense as far as selecting and planting species that are well adapted to our region. But, taken together, tree species native to China, Japan, and the Eastern United States, all places where it rains all summer, make less sense here than species better adapted to dry summers. As my readers are well aware, we have a dry-summer climate here in the Northwest. Thus, I simply don’t think it makes sense to recommend continued planting of thirsty trees. It makes even less sense when we consider that our summers have been on a warming trend and water resources are likely to be increasingly strained over time.

Still, I’m not drawing too hard of a line: some tree species from wet-summer climates perform adequately here, and examples of them can be seen in cities all over the Northwest. Some perform well in Port Angeles but not Portland, since Portland is that much hotter and drier. Some of them perform well but only on good soil: in less than ideal soil conditions they languish and die. For example, Cercidiphyllum japonicum, a relatively popular/available selection from the list, really needs heavily amended or deep, fertile soil to do well here without irrigation in the long run. One could recommended it for, say, Mount Vernon, a city built on deep, alluvial soil. But for much of the Northwest this species isn’t a great choice.

Here is where more problems and inconsistencies pop up. But before getting into that I would say there are large parts of this list I certainly agree with. Many of these trees are inappropriate as street trees and ought not to be used, no doubt about it!

“Large Evergreens” – I can see why something like a 200′ tall douglas fir doesn’t make sense as a street tree. Still, I would think you’d want to allow for quite a few exceptions to this rule, especially for those species which develop dome-shaped canopies, have exceptional drought tolerance, and/or remain compact in stature. I can’t believe they forgot to mention Leyland cypress, the scourge of the Northwest. Also I find it interesting that deciduous conifers and true cypresses are not mentioned here; though obviously they are also not on the approved list. There are a few rather large Monterrey cypresses around Port Angeles, which are on the large side for a street tree but make quite a statement!

The next six things on there are certainly problem trees. However, I would question whether Platanus occidentalis is really so much better behaved than P. x acerifolia, which is on the approved list. My impression is that all Platanus have rather aggressive root systems, but perhaps there is some variation.

Then you get to “palm trees.” This is the part that tells me some snippets of this document were pulled from a completely different climate. I would like to know where in the Pacific Northwest anyone has seen palm trees cause the problems this document accuses them of: invasive root systems, damaging sidewalks, weak wood that breaks easily. In California, larger species of palm trees have moderately aggressive root systems but even these don’t have the capacity to crack sidewalks. Palm trees don’t even form a woody root system. Most problems with palms are associated with species that won’t even grow long-term in our climate (Washingtonia and Phoenix species, mainly). These problems include being messy, harboring rodents, dropping huge leaves and sticky fruit at random, and being a major fire hazard when the older leaves aren’t trimmed off. But none of these issues were mentioned in our document, so I’m just saying let’s be honest about what those problems are.

Most importantly, because we cannot grow those problematic species of palms in our climate, all the concerns about them that I described don’t mean much here in the Northwest. Our most popular hardy palm, Trachycarpus fortunei, is quite well behaved, has never been known to harbor rodents, possesses fruits that are small and not messy, and I’m darned if I’ve ever heard of one catching fire.

Now as far as using T. fortunei as a street tree in our climate, I think that it is too small-scale to be impressive, besides which it prefers summer water. There are some nice ones in Port Angeles (including some right along Eunice St. as street trees) but they can also look a bit weather-beaten with exposure. So to clarify, I’m not advocating its use as a street tree; I mainly want this document to make sense from a horticultural standpoint.

(Now Jubaea chilensis as a street tree, I could get behind! The Seattle Arboretum invested in some large ones a few years back, which so far has paid off as they are looking great [except for people stealing the fronds for Palm Sunday]. It has also proven hardy in Victoria. Notably, this species is native to a summer-dry climate. Of course, one may still complain about the fact that it may take decades for enough clear trunk to be produced that the fronds are above head height.)

So moving on from palm trees, I have no problems with the next bit, although I will say I have noticed quite a few of these being used as street trees in Port Angeles. I find it interesting that Fraxinus are prohibited generally; certain ash cultivars have been very popular street trees in other municipalities, especially in the interior West, and remain so even now with new plantings continuing. Three specific ashes are mentioned and it’s ambiguous as to whether the widely used types should be allowed. Also, as long as we’re considering birch, we may as well ban them all equally since they are all aggressive surface rooters that are greedy for water and can get significant pest problems when they get too dry (though I’ve seen less of this in Clallam County than in, say, Seattle or Olympia, no doubt because summers are cooler).

Moving on to horsechestnut—wait, didn’t we just see that on the recommended trees list? And it’s certainly more LARGE than medium. Also it reseeds itself. It does great here and is very well adapted, but if we are concerned about reseeding potential, we probably don’t want to recommend it.

Fruit bearing trees—mixed feelings here, since there is something to be said for planting fruit trees in publicly accessible places. However the problems with them are substantial: dropping fruit on cars, staining sidewalks, etc. There would need to be some assurance that they will be pruned annually and maintained to fit the space. I don’t expect that to be realistic in most instances.

Overplanted trees: YES! I’m on board with not using any more of these. But let’s add to the list virtually anything else native to a climate with wet summers that is reasonably common—perhaps granting exceptions for a few tough species that still do pretty well here (eastern US oaks, for example). As long as we’re telling people what not to plant, we might as well be consistent!

Ok, that is enough with the critical mindset for now. In a future installment, I promise to offer constructive thoughts on the topic in general, on what types of trees should be used, and will be so bold as to recommend at least a starter selection of appropriate species that would make great street trees in the Northwest.