Selecting Trees: Surviving in Hell(Strips)!

This Liriodendron tulipifera, a heritage tree in my neighborhood, has a canopy over 90' across. It is a beautiful and dominating tree dropping tons of drain clogging leaves and negating any need for actual street trees in the vicinity.

This Liriodendron tulipifera, a heritage tree in my neighborhood, has a canopy 90′ across. It is a beautiful and dominating tree dropping tons of drain clogging leaves and negating any need for actual street trees in the vicinity.  Little can grow in the dry shade beneath it.

I’m a horticulturist, a person trained and practiced in the ‘art and science of growing plants’…a classification to which trees belong. I’m not a ‘tree expert’ though I like to think I’ve learned a few things having spent most of my last 35+ years out working in the landscape, planting, caring for, diagnosing and designing, the bulk of which was maintenance, trouble shooting and tweaking landscapes so that they work ‘better’. Trees were always part of it…so I have opinions.

            [One of the lessons most of us learn on our journey to adulthood is to avoid the topics of religion and politics in casual conversation. These can be very divisive. In Portland the topic of trees can also elicit strong feelings amongst their advocates. The City of Portland has worked toward the protection of its trees. Here we have, in many cases, codified the planting, pruning and removal of trees in an attempt to stop the most egregious offenses and to expand the urban tree canopy. The City, through its Forestry Division, also works to help educate a public that too often has little to no connection to the green growing world. It is a huge task especially when so many other public institutions, like public schools, play almost no role. I spent the biggest part of my professional work life in Portland Parks and Recreation and I know that most Park’s staff have a passion for the work as well, even after years of working in a very political atmosphere with inadequate support. It would wear on anybody. So when I criticize aspects of the City’s tree program I want to be very clear that I am not criticizing the people or their intent.]

Portland loves its trees, except for the malcontents who view each leaf that falls on their property as an affront not to be tolerated, oh, and those developers looking to build and cash in on ever square foot of space that they can appropriate. Yes, these people are out there, just as are there opposite.

People can get very emotional about their trees in this town and once they are planted, they can become very difficult to remove. Trees have recognized ‘rights’ codified in City Ordinance. There is an entire section defined in our ‘Tree Code’. Over the years I have become much more critical of the selection process that precedes tree planting. I love trees, hiking amongst them in forest, wood and savannah, placed so beautifully in our Parks by such pioneers as the Olmsteads and Mische, as specimen in private gardens of which Portland has an abundance, but very often, not along our streets. Sure, there are those neighborhoods like Westmorland with their street spanning canopies of Maple that belie the fact that we are in a modern city. All too often I see poor examples, some that are in the inevitable slide to death and many others that hang unhappily in limbo, tree purgatory, where trees are doomed to stay for years, hanging on, stressed, exhibiting twig die-back, defoliating early every summer, branches broken by parking vehicles or, conflicting with sidewalk space, are broken or ripped down leaving disfiguring wounds that will be with us for years. These are ‘code’-scapes, created to satisfy code more than they are to create an imagined vision of beauty or, alternately, are selected by homeowners with good intentions, this one planting likely being their only opportunity to choose trees for such a purpose. This is where my issue with the ‘process’ arises.

The City wants street tree planting to be a democratic process. It wants residents to feel a sense of ownership that will inspire the continued caring of said trees. It wants residents to have the freedom to choose what they want and to aid this process, has created a series of lists from which residents may choose, that will still meet the City’s needs. This all sounds laudable…but there are problems and they appear to stem from the City’s limited priorities: first and foremost that we increase the proportion of land covered by tree canopy, second, that such plantings not conflict with power-lines and the safety and movement of traffic and, third, that the trees selected are less likely to heave and break sidewalks and curbs. I’m not going to argue against these, as they are certainly important considerations when choosing trees for urban situations, but they are not the only ones and they are certainly not the most important in terms of a prospective tree’s health, which translates to their beauty and longevity at any given site. I will argue that the lists are too ‘simple’ and allow residents to unknowingly, with the City’s implied assurances, choose trees that won’t be good performers, that once they are in, are the resident’s problem. Residents often end up with trees that are bad or marginal choices given the growing conditions on their stretch of ‘hell-strip’, even though they meet the City’s criteria. What am I talking about?

Simply considering whether a given tree has adequate space given the width of the ‘hell-strip’ and the presence of over-head power-lines, is a far cry from assessing a site’s growing conditions upon which the fate of any tree hangs. All plants, including trees, possess a genetically set range of conditions that they will tolerate. Those in which they will thrive are considerably narrower. There is no tree that could be called a ‘sliver bullet’ in Portland, no tree that will perform well whatever the soil and light conditions. Pushed beyond their ‘prefered’ limits trees may perform ‘good enough’…until they don’t even do that. Will they exhibit the vigor of healthy growth and grow into strong structured beautiful examples of their species or characteristic of the selected cultivar? That is entirely different. Trees aren’t that much different than humans in that if you stress them physically by not providing what they need you will shorten their life, by weakening them and thus making them more susceptible to opportunistic diseases and insect attack…and, given that this is an urban area, poorly grown plants are more likely to attract the attention of those of looking for something to vent on. Vandalism rates increase. I’ve seen it often enough. Is this common result good enough?

There are studies out there that have surveyed the longevity of urban trees. I recall a few years ago reading one that pegged the average lifetime of an urban tree at an incredibly short 7 years! Of course that factors in all of the heavily vandalized trees, trees driven down by cars and trucks, trees that came defective from the nursery or were badly damaged during transport and planting, trees that dried out or froze while they sat waiting to be planted, trees that missed establishment waterings, those that were flooded by over zealous owners or contractors during hot/dry periods and trees poorly chosen given their site conditions. The later may be a huge number especially so if the organizations planting have a low expectation of success or simply view growing conditions as minor given all of the other trials and tribulations that a tree will face in its undoubtedly shorter life in the City as compared to the one led by its progenitors back ‘home’. I have no idea what the number would be for Portland today. It does seem rather wrong headed though to assume that the extra time spent selecting a tree for its suitability, is a waste.

So, Joe Public, gets the list, maybe even decides to do the family thing with a community Friends of the Trees planting, the kids are excited, they scan the availability list and make their choices. No one would plant a tree in front of their home if they thought that it would be a poor one…, okay, some still would because they would simply want the tree they have a sentimental connection with, besides, in their ignorance, they can still cling to the idea that it ‘is’ a good choice. Is anyone telling them that it’s a bad choice? Or, that there are better choices? And, I’m not talking about aesthetic choices. I’m talking about roots in the soil reasons.

There are reasons that we call these curbside right-of-way plantings, ‘hell-strips’. If hell is a place for eternal punishment the name seems appropo. These are amongst our most public of our urban landscapes. While they front our homes and businesses, they are apart and sit beyond the more defendable private property that may include our front yards, a thin ribbon of public property and access. These were created as buffers between vehicular traffic, horse, trolley and automotive, and the defined pedestrian space. Over time many streets grew wider to accommodate increasing traffic always cutting away at the space at its edges set aside for residents. Trees, as denizens of forests, woodlands and savannah, could hardly be planted in more foreign difficult sites. And that’s the problem with so many of the trees on these lists, any tree will be challenged.

Typically street trees will be confronted by: a limited volume of soil that will effectively limit all but the most aggressively spreading root systems; generally compacted soil that results from the construction of the road, sidewalk and buildings that bound it, such engineered constructions that may also include buried vaults, but are also compacted by years of foot traffic back and forth to parked vehicles and by the fact that much of this land has been occupied by few plants which can themselves, over time, open the soil as the gradually penetrate deeper; these soils may also suffer from the grading and filling, the upending of topsoil, that precedes urban development, which can result in nutrient poor, mineral soils; all of this leading to a condition of reduced drainage. Keep in mind that all of these trees come from originally, complex plant communities, that evolved on site, creating the soil they prefer as a consequence of all of them being their over time sharing the space and soil. The soils found along streets, in these ‘hellstrips’, are all compromised.

The architecture and grid structure of a modern city itself creates conditions that can make life difficult for plants creating ‘canyons’ and geometric pathways to funnel wind, creating abrupt transitions from built structures to landscape and by doing so creating reflective surfaces that increase the intensity of light and heat that can unduly stress any plant beyond its capacity to accommodate it. It can be hotter, colder, windier, brighter, darker, throughout the year plants can experience changes of conditions akin to someone flipping a switch, where all summer living in reflected heat a tree in winter finds itself shaded all day for days on end. These can be exceptional conditions.

So, what do we do? What am I suggesting? First we need to acknowledge that a large proportion of the trees being planted in our ‘hell-strips’, however well intentioned the planters may have been, are going to have a difficult time. People believe they are doing good by planting trees and, potentially, they are, but they need more guidance, more support. What ever information we can provide them will be better than where we are today. I would begin by addressing the tree lists and ‘beefing up’ the information presented.

If we want to plant a tree, and we’ve taken a serious look at the conditions that our site presents, we still need to know what conditions a prospective tree requires or ‘prefers’. To do this we need to know ‘where’ it comes from and I mean this in terms of the specifics of its preferred sites and the broader geographical, location, climate information that characterize the ‘range’ within which the tree ‘evolved’. Each listed tree could have a clear, concise ‘description’ of where it comes from and its preferred conditions. In some cases, trees can ‘surprise’ us buy being unexpectedly adaptable to conditions that are not readily assumable. In these cases, such proven performance, could be noted and a + or – used to indicate whether it tends to be more or less tolerant. As this is a Portland list all selections will be cold hardy to 7b. Trees that have proven out on the ground, though they may be 8a could be listed, but noted as such.

This Gingko biloba, planted about 15 years ago, is still small by Gingko standards, but has been doing very well even with next to no supplemental water.

This Gingko biloba, planted about 15 years ago, is still small by Gingko standards, but has been doing very well even with next to no supplemental water.  There are several scaffold branches 4′ – 5′ above the ground.  These will become problematic in such a narrow planting near the street as they caliper up.

The following are examples of trees, already on the list

Amelanchier grandiflora ‘Autumn Brilliance’) – hybrid of East US; sum wet; woodland; well drained; sun-pt shade;zn 2; very suscept Rust; stunted in hell strips

Franklinia alatamaha – SE US; sum wet; hot/humid, riparian woodland; ex. drain -; full sun to aft. shade; zn 5-8; difficult.

Fraxinus pennsylvannica – E US & Canada; sum wet +; forest; full sun; zn 3, adaptable

Gingko biloba – Japan, China; sum wet +; forest; moist/deep/sandy soil +; full sun; a very tolerant urban tree.

Styrax japonicus – Japan, China; sum wet; forest; moist/humus; sun – pt shade; low horizontal branching

Another list could be kept of trees proven to be tolerant to xeric/no irrigation conditions found typically in ‘hell-strips’, or so noted, so that planters wanting to go this ‘direction’ would be able to choose from a reliable list.  This list would be somewhat ‘experimental’ in nature as trees would have to be evaluated and rated in ways they have not been previously.

I’ve grown the following in unirrigated, compact fill with significant slope.  Others are experimenting as well with success.  Such a list could be greatly expanded upon.

Arbutus menziesii – Native west coast Washington south through most of California; forest to grassy savannah; ex drainage +; summer dry; sun to pt shade; no summer water!; generally difficult to grow to size in a nursery/ intolerant of transplanting

Quercus chrysolepsis – Native west of Cascades & Sierra Nevadas, south of Eugene; sum dry; savannah to Oak woodland and Mixed Forest; heat tolerant; sun.

Quercus garryana – Our native Oregon White Oak, a potentially large grower

Quercus hypoleucoides – Mtns. of southern Arizona into Mexico; seasonally dry; tol or some summer irrigation

Quercus wislizeni – Native to much of California from the foothills of the Sierra Nevada almost to the coast, full sun; often in rocky soil but tolerant; no summer water after establishment.

I’ve also planted, in smaller numbers: Quercus douglasii and Q. suber (the Cork Oak).  There are many mediterranean trees that could prove very useful in our ‘hell-strips’ and others that have been surprisingly very effective…many of which aren’t on the list.

These Franklinia and Gingko represent two extremes on the scale ranking probability of success from nil to almost falling out of bed easy. While the Gingko comes from a forested summer wet/monsoon climate, with deep, moist, well drained soils and sun, conditions the Franklinia would prefer/require, the Gingko has proven itself to be much more tolerant on much heavier, more poorly drained soils, in harsh urban conditions. This tolerance is indicated by the (+) signs. The Franklinia is assigned a ‘-‘ because it is very narrowly tolerant and so is described as difficult or demanding. It would be nice to be able to graphically show the differences to show prospective planters. In the plant world, Franklinia is one of those plants that can test the abilities of an accomplished plants-person. It causes me to wonder why it’s on the street tree list. Yes, it is a beautiful plant in and out of flower, which are individually gorgeous. If one is looking for that kind of experience one should be searching out the new bi-generic hybrid x Gordlinia grandiflora a cross of the aforementioned Franklinia and another southeastern native Gordonia lasianthus. If you can find one, and it won’t be very big when you do, it is purported to be more amenable to growing conditions, still, a ‘hell-strip’ would cause me to hesitate on this one, save it for the back garden.

Part of this process should be to educate tree planters as to what their own site conditions are and how that matters. When selecting a tree people need to know that we live in a region with warm/dry summers and cool/wet winters and that this is important to understanding how trees from other climates may be stressed here, especially if we don’t intend to adjust our care in ways to better suit them, e.g., regular summer irrigation, indefinitely if you want such a plant to remain in good health with vigor. Not getting what any plant prefers will stress it and affects its performance over the long term. Our climate, in terms of when our precipitation occurs, is opposite that of summer/wet/monsoonal climates. In this situation, depending on the particular plant, it may bake and dry out alarmingly in summer and then be subject to cool wet soil all winter that may create fungal problems and root rot.  At minimum it should be noted that winter deciduous trees will be unable to photosynthesize here when soil moisture is supportive of it.  That is a huge deal!!!

This Stewartia pseudocamellia has been here for almost 20 years. I'm surprised by its trunk size as its leaves scortch early ever summer, has suffered much vandalism/breakage and an occassional, inexplicable clunky pruning job.

This Stewartia pseudocamellia has been here for almost 20 years. I’m surprised by its trunk size as its leaves scortch early ever summer, has suffered much vandalism/breakage, twig die-back and an occassional, inexplicable clunky pruning job.  This Stewartia is a woodland dweller from summer/wet Japan that is dependable in our gardens with good soil and summer irrigation.  Not so much in ‘hell-strips’.

Seeing that a plant’s natural ‘community’ is a forest situation, or along a river, riparian, suggests that a street setting may be too harsh in terms of light, heat/dryness and soil moisture. Plants that have evolved with deep, rich, moist alluvial soils along a river may not be a good choice. On the other hand, a few, surprisingly, have been. Trees like Nyssa sylvatica and Taxodium distichum both from SE US from hot summer wet climates (humid sub-tropical) have proven to be quite adaptable here to unirrigated conditions where soils are deeper, as street trees with limited soil volume??? Maybe not so much! The very similar in appearance Metasequoia glyptostorboides, from similar conditions in China, has demonstrated similar adaptablity (Note that a planting of these in the highly engineered conditions found in the center median on the rebuilt Naito Pkwy, struggle.) You can’t expect any plant to adapt beyond its capacity, its gene set limits.

I see Magnolia ‘Galaxy’ on the list and have seen it planted in larger numbers along the new MAX Orange Line. I wrote of it on my first Blog posting on the Landscapes of the Orange Line. Like many of the Magnolia species and hybrids, these are forest type trees, from a summer rain region. I was surprised to see them used there given a highly engineered site, i.e., compacted small soil volume for rooting, with broad hard surfaces to reflect light and heat. I don’t think I’ve ever seen them used this way and have serious doubts about their ability to thrive under such conditions. Yes, these are beautiful trees. Yes, they may be plenty cold tolerant, but the immediate environment and soil conditions???

Then there are all of the trees normally associated with the Eastern Hardwood Forests, which are rich in the trees we commonly associate with ‘shade trees’, trees that often show tremendous cold tolerance, trees we have a certain familiarity with, at least those of us of European ancestry. In part, because of this familiarity, we gravitate toward their use along our streets. We have a tendency to bring along the familiar as we move to new areas…there is a comfort factor in operation, but again, as I’ve mentioned elsewhere, there is the availability issue as well, because so many regional growers produce these trees for back east and so they are offered to buyers here, not because of their appropriateness, but because of these two factors and their ‘hardiness’. We are sold on their ‘hardiness’. Perhaps because so many of us come from colder areas in this country we find comfort in trees that are cold hardy to temperatures we will literally never experience here, ever. Many of the trees we plant can accept winters that plunge to ‘0’ and below every year and not just single random events, but sustained cold periods that typically last for weeks or months. The early 1950’s was the last time the Portland area came even remotely close to these conditions. We need trees that are adapted to our conditions.

One of the most difficult things that plants here face are the sudden temperature swings in winter from periods of relatively mild, above freezing minimums, to sudden quick drops into the lower 20’s, after which we can remain mild for most of the remaining winter. Our temperatures, as a result of our location, near the Gorge with a maritime influence, tend to ‘yo-yo’ up and down, teasing plants in the process between freezing dormant temperatures and more mild, growable temperatures. Our minimums literally never drop below freezing for months at a time…yet we plant these very cold tolerant eastern hardwoods? Extensively! None of these trees, by definition evolved here on the west coast with our decidedly mediterranean type climate with mild wet winters and warm dry summers. The fact that these trees may in many cases do ‘okay’ should be looked at a little closer.  Given these common winter conditions here, it should not be surprising that many of our best native performers, away from riparian zones, are evergreens, that are as such, always ready to photosynthesize when temperature and moisture allow.

The Willamette Valley, as a region, has some of the deepest, most fertile soils, in the US. We also have a relatively mild climate and adequate reserves of water. Note that I said ‘reserves of water’, because our precipitation does not occur during the prime growing months of much of the stock that we produce. This is what lends our region to be such a successful and significant producer of nursery stock. We can grow almost anything here, and often, more quickly than most places in the country. The historic plant communities of our Valley reflected our conditions. A visit in mid-summer would have demonstrated this in its broad spreading meadows, savannahs and woodlands that were passed their spring prime already moving into the seed production that follows early flowering. Meadows, depending on their local water conditions would be beginning to take on their summer dormancy turning sere. Our regional richness of conifers and broad-leaved evergreens would be demonstrating their adaptability, their readiness to grow whenever water is availability by hanging on to their leaves and photosynthesizing when conditions permit. Much of our woody deciduous flora would be huddled along rivers, creeks and draws, sloughs and bordering our many broad wetlands. Big Leaf Maple would occupy mixed forested areas where soil depth and moisture allowed it. Garry Oaks would have spread across the valley in deep soils that permitted its roots to find adequate moisture at deeper levels.

‘Eastern’ trees evolved with regular summer rains. True, many lived in river valleys, superficially very like our situation here, but their summer-wet climate supported such growth. In fact, if you study it, deciduous trees, overall, have their advantage where soil moisture is consistent in summer time. They produce their leaves each spring, at great expense to the tree, photosynthesize throughout the summer and then shed them with the onset of the sustained cold of winter. In their home ranges it is the cold that is the limiting factor in growth. Remember, here we have a richness of evergreens, with relatively mild winter temperatures that can still allow photosynthesis and this is when the moisture is most available. For many of our native plants spring and fall are the seasons of most active growth. Summers can be defined by drought dormancy. Over the millennia natives here evolved to adapt their growth cycles to our dominant conditions…as is true in any region.

The takeaway from this is that if you want to grow healthy vigorous trees that are native to the Eastern Hardwood Forests of the US, you need to accommodate their needs, soil and moisture, throughout the year. By not doing this we grow mediocre, though maybe ‘adequate’ specimen. If local conditions are too severe, an inadequate available soil volume, drought conditions with desiccating summer heat and wind, plants may die or be so stressed that an opportunistic disease or insect may do them in. Remember that poorly grown plants are less likely to be able to ward off threats that a more healthy plant can take in ‘stride’. There are many great examples of these trees here and they are often residents of landscapes that offer a broad expanse of soil for their roots to occupy and may in fact be irrigated. There are many others that, at least to the discerning eye, limp along, their canopies waving overhead like distress flags, smaller than normal leaves that regularly begin to ‘burn’ by mid-late summer and stunted twig growth characterized by short internodes. In my way of thinking, especially if we are trying to be more attuned to our local conditions and are converting our landscapes to those that will be more sustainable in terms of long term maintenance, we will begin to choose trees that are more adapted to the conditions that exist here. Because this is a highly urbanized landscape, with often severely compromised conditions, this does not limit us to only a native palette, in fact, these compromised conditions have already proven to be very difficult to simply ‘switch’ to a native palette. We should be broadening our look to, hold on to your socks, the many trees in the world that come from mediterranean regions. People are already doing this locally, we just need to ramp it up and begin adding some of these, especially the ones that have been proving themselves here, to the official street tree lists along with the descriptors I’ve already mentioned, to again, educate the public and demonstrate to other professionals that their are other, better, alternatives to the old tried, but not always so true, standbys.

There are many individual cases where I could quibble, but I want to touch on three other issues. First, as a gardener and someone concerned about our energy future and livability issues here, I want to suggest that planting trees everywhere is only one response to our many conflicting and ingrained problems that we face as an urban community. As our population continues to grow and our density increases, we need to have a serious community wide discussion of limits to our growth.  All living systems and organisms have limits.  Growth imposes stresses and strains on systems and organisms.  Carbon sequestration is one need.  Food and energy are two vital others.  We must also provide solar access to grow more of our own food locally and to produce electricity and provide for some portion of the heat we require to warm our homes and heat our water. Canopy cover negates both of these opportunities. It also seems a little wrong headed to only focus on shade trees that help cool, through shade, our homes in summer, while we continue building out the ‘urban heat island’ and driving carbon spewing cars everywhere. Trees, are only part of the answer.  Enough on that here.

A neighbor's Dogwood planted in a narrow parking strip. It has no space to grow into.

A neighbor’s Dogwood planted in a narrow parking strip. It has no space to grow into.

Another issue is that there is only so much space available for trees, Many of the curbside ‘hell-strips’ are simply too narrow. A 2 ½’ or 4’ wide space, especially if there are overhead wires, gives any tree choice very little space to grow unless it has an extremely upright habit or form. I see small growing trees regularly planted in such narrow spaces now, like my very own Autumn Brilliance Serviceberry, as well as small growing Cornus and Styrax, that are compromised through pruning into ugliness. Small trees still have a particular form. They occupy space. While some are more malleable than others heavily pruning a small tree to fit a space can destroy many of the aesthetic attributes that the tree has to offer. Small trees tend to branch low. Normal growth of branches adds to a tree’s width, width that can and does immediately conflict with adjacent sidewalk in these narrow spaces, remember that there must be 7’ of clearance over sidewalks. This effectively means that your low branched tree cannot extend toward the sidewalk anywhere below 7’, from that point it can extend horizontally into the space. On the street side the limit is 11’ below which a tree, by code, cannot enter the space to conflict with traffic or parked vehicles. This can be even more problematic for trees that respond with lots of sprouting or are susceptible to dieback when pruned hard in this way.

There are 4 of these Acer griseum, Paperbark Maples, in this planting that are growing with some vigor. Planted along a west facing strip they receive some protection by the structure and trees across the street. There growth is restricted to a very narrow space and are growing in a nearly 'flat' fan so as not to conflict with the sidewalk and street. This exposes a very ungainly structure.

There are 4 of these Acer griseum, Paperbark Maples, in this planting that are growing with some vigor. Planted along a west facing strip they receive some protection by the structure and trees across the street. There growth is restricted to a very narrow space and are growing in a nearly ‘flat’ fan so as not to conflict with the sidewalk and street. This exposes a very ungainly structure.

These plums, restricted as they are to such a narrow space, show their ungainly branching. These are unirrigated and show stress every summer as well.

These plums, restricted as they are to such a narrow space, show their ungainly branching. These are unirrigated and show stress every summer as well.

Many trees simply don’t have the genetics or stature to grow in such legally defined space. Actually probably none do if they are also limited by the presence of overhead wires. Perhaps in our zealousness to grow the urban canopy we are pushing up against our own built limits. Urban areas, especially if they are undergoing a process of densification and infill are going to be extremely hard-pressed to keep growing the canopy. The only way that can happen is to set aside an increasing amount of ‘greenspace’ in the form of parks, greenways, wildlife corridors etc. There is only so much space and it cannot serve every need. Many functions obviate others.

As a part of this effort it would be beneficial to have a searchable data-base, it would not have to be complete, to give homeowners on-line access to so that they could find healthy examples near them of plantings which have proven themselves over time. This would serve to educate the public and make them better, more active participants, in the growth and care of our urban tree canopy/forest.  Oregon State University has a very good descriptive list of many species and cultivars, the City’s list links to it, but it is without ‘performance ratings’ for ‘hell-strips’.  It does tell readers where they can see in ground examples…on the OSU campus in Corvallis.  Such a local database could begin with Hoyt Arboretum (most of the plantings here are maintained without summer irrigation, though the conditions would be less extreme than found on ‘hell-strips’) and Parks that maintain databases of plantings.  The City’s Forestry Division could establish a database specifically for ‘hell-strips’ as these areas are in their purview.

It would also benefit the community in general if the City reviewed its lists of recommended trees to address the problems I’ve described above. Residents plant trees with good intentions and, very often they are dependent upon these very lists to make their choices. If trees are to perform in a healthy manner in ‘hellstrips’, it should be made clear to residents which ones are at a climatic ‘disadvantage’ here so that they can decide whether they are committed to their long term care and irrigation.  Which trees are the proven performers in difficult situations?  I’ve spent most of my life involved with plants, one way or another and, sadly, am still surprised at the level of uninformed ignorance amongst the general public.  It drives home the fact that we as a society now largely live our lives removed from the growing world and because of this, believe that plants/trees are interchangeable, that there requirements are simple and limited, that they don’t require our participation, that they are some how separate, that they will grow or die despite our efforts and it is beyond our knowledge or abilities to even involve ourselves.  People need help making their selections.  There is nothing in our genetic codes that ascribe the needed skills and knowledge to us.  And, it is important that we make good choices.  It is important that we begin to wake up to our responsibilities as urban dwellers in a very changed world, a world that is every day we are making more subject to our own choices than the needs and requirements of the biological community, that though damaged, we are still a part of.  if the City wants to be a leader in terms of sustainability, it should offer more ‘sustainable’ tree choices and attempt to educate the public why that is. Otherwise it is just more political posturing without substance.

Parrotia persica has become more popular in recent years. Strongly vase shaped these can become quite broad over several years. Mine is 25'+ tall and a good 20' wide. This one branches low to the ground and will quickly be in conflict.

Parrotia persica has become more popular in recent years. Strongly vase shaped these can become quite broad over several years. Mine is 25’+ tall and a good 20′ wide. This one branches low to the ground and will quickly be in conflict.

But it isn’t just our ignorance of trees that causes us problems during the selection process and ‘establishment period’, most people need help as well with how to care for them as they grow into their mature size.  Trees will each respond to the light and space given them in their own way.  Any tree grown in a forest or dense woodland situation will tend to grow more upright, more quickly, the lower branches yielding to those higher, lengthening the trunks, effectively raising the canopy, without any intrusive pruning.  Plant the same tree in the open with adequate sunlight and it will begin to broaden its canopy lower, often with large caliper branches quite low on the trunk.  Such trees will need pruning to produce a higher canopied tree that allows for activities like play or walking or even access to one’s car.  Waiting too long results in large wounds when the removals are finally made.    Not removing them can cause direct physical conflicts or give us the sense of being closed in.  It is a balancing act of what the tree needs and what we need as ‘residents’ of the same community.  This lack of knowledge results in many conflicts which generally results in greater injury to the trees.  Responsibility does not end with planting and establishment.  It is a life long commitment comparable to owning a home, pets or even having children, in which shirking responsibilities will have real world consequences.  Think of it not as a burden, but like these other responsibilities, one that can enhance our lives.

This row of 20 year old maples received to structural pruning in their youth resulting in large cuts/wounds when they were finally dealt with. One of the original neighbors, an arborist, moved a couple years after the planting and the other owners didn't recognize the need.

This row of 20 year old maples received no structural pruning in their youth resulting in large cuts/wounds when they were finally dealt with. One of the original neighbors, an arborist, moved a couple years after the planting and the other owners didn’t recognize the need.

The issue of urban canopy and street trees exists in the real world of competing desires, needs and functions. Cities are very complex and a politics where advocates of one group push more successfully than others can result in the diminishment of the goals of the others. Affordable housing, compact cities, urban tree canopy, food production, energy conservation and regional self-sufficiency, local healthy food systems, public spaces that are supportive of community and individual health, an economy that both meets the needs of its residents and provides meaningful work as well…all of these and others need to be addressed. For many the issue of street trees is relatively minor, not so for others. If we are working toward the creation of a city supportive of the life that it contains, all of it, we need to look at our commitment to tree canopy and its component parts. Not all trees are created equal. Many will place demands on the environment that cannot be met. Others can be planted, if conditions are weighed, that will contribute more than others might over the course of their relatively long lives. Trees, as living organisms, require support throughout their lives if they are to be ‘successful’ and contribute to our overall well being.  If we are going to plant them trees should ‘fit’ because these will both place less of a ‘burden’ on us in terms of their care and replacement and because by ‘fitting’ they can grow as they ‘should’ and in so doing contribute to the beauty that we all need living in a city that can too often be characterized by utility and neglect. If we can equate beauty with health, and I think that we must, all of these incremental decisions that we make along the way creating this place in which we live, need to reflect this pairing. Beauty does not merely happen as a result of random process. Nature, undisturbed, contains a kind of genius that directs its growth. In cities we have largely broken this process, but there is no reason that we can’t learn to reengage with the natural world, to stop using it and begin facilitating it. I view this as an absolute essential.

I encourage all of you to look at the fine book, Trees for all Seasons: Broadleaved Evergreens for Temperate Climates, written by our own Sean Hogan, one of the truly exemplary plantsmen on the west coast. Not only are his descriptions thorough and engaging but he provides the contextual info that can help any of us make better, more informed choices. Sean also has a recent article in Pacific Horticulture Magazine, “Oaks are the Answer: Right Tree Right Place”, an excellent ‘introductory’ piece to his book and, in general, his ideas about trees for the Pacific Northwest.  We could all stand to learn from him and those others out there asking questions.


1 thought on “Selecting Trees: Surviving in Hell(Strips)!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s