Adaptive Management and the Dynamic Maintenance of Sustainable Landscapes


The second grassy bay, below the Harborside Restaurant, between the Taxodium clumps from the south end. A sweep of Cistus pulverulentus 'Sunset' at the bottom, Ceanothus cuneatus 'Blue Sierra' at the left and two Arctostaphylos x 'Harmony'. The grasses are Kohleria macrantha, native, Festuca rubra commutatta and a few nasty invaders.

The second grassy bay from the south end, below the Harborside Restaurant at Riverplace, above the marina, between the Taxodium clumps. The ’04 planting included no shrubs or perennial forbs in this area.  It was a monoculture of Koeleria macrantha, a native early season bunch grass that goes dormant by mid-July leaving the entire area vulnerable to invasion by weeds and offering no ‘barrier’ to either people or dogs, which enter frequently. A sweep of Cistus pulverulentus ‘Sunset’ at the bottom, Ceanothus cuneatus ‘Blue Sierra’ at the left and Arctostaphylos x ‘Harmony’ have been added to this site along with Festuca rubra var. commutata a low, fine textured spreader to help fill in the spaces and scattered native perennials.

We, all of us, are part of the landscape.  Just as individual plants belong to a local native plant community, and its place, so do we. That we live in highly disturbed and contrived landscapes does not change the fact that we live in relationship with it, that we are a functioning part of it. Deny this as we may, many of us as a group likely admit to very little connection to our ‘place’. It’s just where we live, for now. Our understanding of it and any involvement with our landscape, other than as a simple stage for our lives, is minimal, a condition which has become pervasive in modern society. Some professionals, who work with children have come to refer to this state as NDD, or Nature Deficit Disorder, a dissociative relationship now that was once basic to human survival. Today this condition is pervasive and our landscapes, as a result, severely disturbed, damaged and compromised, lack the capacity to return to their former state. There is a general ignorance amongst the public and our leaders of the severity of the problem and our necessary role and responsibility to correct it.  We are locked into a strategy that views landscape as incidental, the natural world as backdrop for our activities, not central to our well-being.  Today landscapes, as long as they meet our grossly simplified idea of our needs, a modern minimalist aesthetic, that does not over tax our ‘pocketbook’, are forgettable. From a horticultural viewpoint this is becoming an increasingly deteriorating disaster, something that not only we can do something about, but one that is imperative that we do so.  Adaptive Management describes a responsive relationship between people and the place in which they live. It is centered on a positive and workable strategy we can adopt that addresses this situation and turns it around, reengaging us with our landscape.

If we look at landscapes as living dynamic systems, not as some fixed in time iteration of a designers’ plan, we must re-evaluate our entire maintenance strategy which goes to defining our relationship with it. Traditionally maintenance has been a ‘negative’ process of limiting and control, confining the landscape to the designers’ intent…the design as endpoint and final objective vision. Maintenance, then, is the removal of all that does not belong and the control, or limiting, of the various elements of the plan to stay within design parameters. Contrastingly, the concept of adaptive management is a dynamic approach that seeks to support a more natural ‘balance’ over time given site conditions, the flow of energy and resources in, out and within the landscape, the particular mix of living elements comprising the landscape and the nature of their changing relationships, all within a landscape’s real world context…for my purpose here, an urban one. Adaptive management works toward an evolving  ‘ideal’ instead of toward a fixed in time vision.  Traditionally maintenance staff could refer back to plans and photos and keep to a schedule to hold the landscape within tolerances.  With adaptive management, especially when one’s goal is a sustainable landscape, there is an ‘idea’ that you are working toward.  The plan, is a starting point, the designer’s best shot.  Maintenance now becomes a process wherein staff ask themselves a never ending series of questions in an effort to determine what they should do next and to evaluate what it is they should do next.

There is a process here that will be common to all landscapes.  Without some kind of formalized process, we will be ‘shooting in the dark’ and the work and intentions of those whom we follow will likely be missed, forgotten or ignored as will be their understanding of the site.  So first:

  • Site analysis – Understand the existing conditions, functions and values, with an emphasis on a site’s ‘history of disturbance’ and the ongoing ‘urban pressures’ human residents apply
  • The ‘Desired Future Condition’.  Adopt a ‘goal’ for the landscape that will move it toward a more balanced, healthy and sustainable future with the understanding that most urbanized sites will probably never be returned to their original, undisturbed state.  Restoration of specific ecosystems will likely not to be possible in the highly ‘disturbed’ urbanized city, so alternative landscapes must be developed that are relatively complex and stable, that ‘fit’ the conditions of their unique urban sites and the needs and reality of a dominating human population while attempting to provide habitat for resident wildlife.  Ignoring the human factor will doom any landscape.

The next stage will be an ongoing, cyclic, series that may be more formalized so that there is a written record of the work on site to help ensure that their is continuity as staff changes.

  • Assessment – Identify the gaps between the existing and the future conditions.  Are our attempts to bring about ‘balance’ effective? This will help us set reachable goals.  As a result of the assessment the Desired Future Condition may be redefined.  This may lead to a different Prescription.  More commonly, the Prescription will be changed over time as the landscape changes or our understanding of our impacts call for it.
  • Design a Prescription – This includes both the landscape design and a maintenance plan that will move the landscape toward the desired future condition.  The maintenance plan can be very specific.  It can be tailored to problematic species and define in detail our approach.  This must be clearly understood if any progress is to be made over the short or long term.
  • Intervention or, the ‘Work’ – Communication is essential between all of those participating in the work.  One person working out of sync may disturb the site in such a way that others misunderstand their overall impact and make ‘wrong’ decisions based on that.  Such a situation can also lead to lost opportunities because in living systems unintended changes cannot simply be erased.  There are no do overs.
  • Monitoring – This is ongoing and continual. Monitoring should occur whenever we enter the landscape.  It is not a function to be carried out by supervisory, management or design staff alone.  Field staff, gardeners, know the specifics of what they have done.  Their site/work familiarity is essential.  It may included formal written reviews, botanical surveys and photographic documentation.

Together these last four ongoing ‘tasks’ comprise ‘Adaptive Management’. These will all overlap.  Communication between all of those involved is essential and ongoing.  Changes in the prescription should be clearly defined, recorded and communicated to all of those involved in the work including ‘why’ a change in course has been made.  The process is the same whether it is a one person operation or many.

Site Analysis: where we are now

Site analysis is essential to both the traditional approach and the practice of adaptive management.  Historically site analysis has been used to establish the parameters within which the designer/Landscape Architect (LA) works, and once the original design is implemented, it is set aside until such a time as a more formal redesign is called for, when either maintenance has failed to ‘protect’ the original design from the active ‘forces’ on the site, causing it to degrade to the point the design intent is lost, or until that time fashion, changed use or ownership calls for a design change. Adaptive management is focused on an ongoing monitoring and reassessment of the site from the moment the project has been installed.  It shifts much of the control/implementation to the horticultural field staff. Ideally, this would be a collaborative approach. Design and maintenance have traditionally shared an unbalanced relationship that has added to the problems our landscapes suffer today. This changed approach may make many designers/LAs uneasy because it requires some relinquishment of control. There is a lack of trust on both sides stemming from their old relationship. This new model requires much more from both sides if we are to start moving toward landscapes that are truly sustainable.

Today, the business of landscape architecture and design, requires a degree of certitude, a single minded vision, to win over clients, that actually works to impede our movement toward sustainable landscapes. In an urban setting we don’t ‘know’ exactly what a sustainable landscape will look like for a particular piece of land. There are too many unknowns, too many elements that have been changed over the years and clients, visitors or users, with expectations of, and relationships with, the landscape that are out of balance…unsustainable, themselves. Today, very often the LAs and designers, through their single-minded vision, attempt to convince the client that their concept, vision and design is the correct one, or at least, the best one. What follows is an insistence that it all be implemented exactly. It is not just a matter of ego that they do this, which maintenance staff may interpret this as, but as a guard, that should the design fail in the client’s eyes, they have a defensible position, because they need to continue to work, to get new jobs. They also do this because landscapes are incredibly complex and their knowledge and comfort level with horticulture is necessarily limited. This is coupled with their mistrust of the abilities of horticultural field staff.  As a result they push to simplify the design in the belief that it will be both easier to implement and maintain. So, like most of us, there is a discomfort with the unknown working powerfully here.

There are three different parts to this problem, first and most important to my purpose here, is the maintenance model itself as this will require a huge shift in approach and corresponding shift in the knowledge and the skill set of those doing the maintenance; second, is a restructuring of the relationship shared between the maintenance staff and the LAs or designers if we are to purposefully move toward a more sustainable practice; and third, an education component for the client and broader public who will ‘use’ the landscape.

Around 21 years ago, (almost 30 years ago now in 2023) when I was still in my early years with Parks, maintaining properties from smaller grass and trees landscapes like Trenton Park all the way up to large more ‘natural’ areas like the 100 acres of Kelley Pt. Park with many in between, Cathedral, Columbia, Pier and east and south to Dawson and Woodlawn, I took a class at PCC Rock Creek on Wetlands, taught by instructor Mark Wilson. An increasingly popular theme was developing in the world of those working in the public landscape, ‘Nature in the City’, with seminars, workshops and presentations for both academics and those of us doing the work on public lands. This particular class was small comprised of students who were working professionally, in some capacity, in the landscape world. Wetland delineation, zonation, mitigation and restoration took up much of our time. We looked with some detail into zonation and inundation, at the ‘banded’ plant communities lying in contours determined by the soil’s time spent inundated, immersed, by an adjacent body of water or as a giant wet sponge absorbing surrounding runoff.   Wilson had been spending years in the field working on the management and restoration of Willamette Valley wet prairie habitat, those many thousands of acres that once served as a sponge and buffer of the uncontained Willamette and its tributaries rising and dropping over the year, so we spent a fair amount of time discussing the problems he had run into on these projects and what we might do to address them.

A particular discussion always stands out in my memory, the problem of weeds and invasive plants: is eradication possible? If not, do we simply engage in the endless ‘battle’ of keeping them under control while seeking to maintain the purity of the native plant communities that ‘belong’ on a given site, or, with all of the intended and unintended changes we have brought to this place, do we look for a different model, a different landscape, that can belong here much the same way that the native prairies and other places once did? This has been one of the driving forces in my thinking in my landscape work ever since.  Weeds sit at the locus of all of the changes.  How do we move ahead? (For an interesting look at this issue see, The Rambunctious Garden: Saving Nature in a Post-Wild World, by Emma Marris, Bloomsbury USA 2013. A more thorough and academic look, though still accessible, at the issue of our altered and evolving landscapes can be found in the book, Novel Ecosystems: Intervening in the New Ecological World Order, a collection of articles written by a group of professionals, researchers, practitioners and policy makers , including the aforementioned, Emma Marris.  The book is edited by Richard Hobbs, Eric Higgs and Carol Hall, from Wiley-Blackwell, 2013.)

We need to begin any project with a look at where we are. The original landscapes and the ‘forces’ at play that helped sculpt them.  Next we need to begin to layout those things that have changed. The bigger and more numerous the changes, the more altered the ‘finished’ landscape will be from the native ‘original’. Important to this process is an understanding of the relationships in the landscape, especially those essential to the complexity and balance of the overall landscape. Not all elements, plant, animal, etc. carry equal weight. Some may play a key role. Once we have ‘defined’ where we are we must do the the same by defining some attainable set of future conditions….A goal.  

Without this our approach will likely be a scatter shot with a frustrating lack of progress.  What must be understood early on is that this is a process with a goal that is subject to change as we  work toward it.  Likely some of our efforts will be futile or even exacerbate the problems on site.  It may be a very complex path. The danger is that we become lost in a mental exercise that never ends. If we chose to take this on we will need to be able to suspend our need for certainty…and that is a major barrier in our culture. What we can be certain of is the overarching goal, that of a complex sustainable landscape.  What that means exactly and how we get there, is the challenge.

Defining Sustainable Landscapes

Sustainable.  This is one of those words being bandied about by everyone from those working in the biological sciences, politicians and economists to marketers and self-promoters of every stripe.  It is in danger of being rendered useless in questions concerning our landscapes. (See an earlier posting on ‘Blurfilication‘.) Sustainable, refers to a place or action that puts no adverse burden on the whole and so can continue indefinitely.  It presents no drain on our resources or capital that will diminish them in the future.  Energy and resources can be used in such a system, but only at a rate no greater than that at which they are being replenished.  They are not drawn down.

It is a word gleaned from the living undisturbed world by those working in the ecological sciences to describe the persistence of native populations, landscapes or habitats to continue over time without human intervention, in a stable though dynamic way, over a period of several generations of its various resident species.  A sustainable landscape/system shows a persistence and resilience, amongst its many species’ populations, that though they may rise and fall, do so within parameters that over time, are cyclic, and are at repeatable, levels.  These numbers aren’t precise in the strict bookkeeping sense as they adjust themselves to the conditions in the changing environment.  Natural calamities are absorbed in stride although there may be those which are catastrophic, of a massive scale, i.e., meteor strikes that may require thousands/millions of years to ‘recover’ from, with adjustments due to species extinction; devastating wildfires and massive landslides.  Sustainable landscapes are closed, in a systems sense, they do not import energy, resources or numbers from other landscapes (There is a very slow migration of species that occurs normally though depending on the landscape’s isolation this could be in the range of one species in a thousand years or so.)  These are stable landscapes.  Needless to say our ‘built’ landscapes, especially our urban ones, have been so ‘disrupted’ that they are incapable of this process of ‘self-maintenance’ or internal sustainable action, they are in a state of flux, of constant change.

[It is entirely possible, and in fact, very likely, that the ‘changes’/disruptions that we have brought to the landscape are already, if we would but step away, working toward a new or novel landscape that is working toward a cyclic, stable state, which we are too close to to discern.  It is difficult for us to see patterns and cycles whose spans are longer than our own lives.]

The physical conditions of any urban site have been changed from the soil up.  Composition, soil grade, drainage, tilth…all of the things that comprise a living soil…are changed.  Plant and animal species in urban landscapes are a result of contrived designs, the heavy impacts of our living here and an established weed population, all of which exists in a ‘chaotic’ relationship.  Populations can change drastically over short periods of time.  The stability of entire landscapes are subject to our limited attention span, whim, fashion or simple opportunity.  The landscape is reduced to simple object, subject to our disinterest, passion or demands.

It would be instructive to look at a mostly intact native landscape to get an idea of the adaptive management approach to landscape maintenance before plunging ahead with a completely contrived modern urban landscape.  On the face of it, such relatively pristine sites, as they exist in a state of natural balance, all parts in relationship to one another, this would seem to be a relatively simple task.  Site analysis and Defining Future Conditions would be fairly straight forward.  Initially any ‘stickiness’ will be in the Adaptive Management phase, specifically in the Prescription and Intervention phases.

A Day on Dog Mountain: Intact Native Landscapes and Adaptive Management

Dog Mountain's upper meadow with Balsam looking across the Columbia to Oregon.

Dog Mountain’s upper meadow with Balsam looking across the Columbia to Oregon.  These are not Dandelions. (Photo courtesy of John Long)

May 15 last year, 2014, I went on a hike with a friend doing the loop up Dog Mountain in the Columbia River Gorge National Scenic Area all of which is protected from development.  We took the steeper approach trail going up returning on the longer, less steep Augsberger trail with its more western exposure and plentiful supply of Poison Oak.  Much of the approach trail is covered by full tree canopy limiting and helping define what was growing on the ground layer.  The trail tended to be several feet wide here in many places as the growth was more open.  Hikers straying widely from the trail tend to stomp out the relatively fragile herbaceous growth.  Still there was much to see from Calypso and Phantom Orchids to Rattlesnake Plantain and Vanilla Leaf.  Significantly, in my memory, there were few to no weeds.  As you approach the top the tree canopy gives way completely and there is a large natural meadow spotted with a basaltic ‘balds’ and their very different plant communities.  Serviceberry fronted much of the forested edge.  The meadow spread out and upward from us in a complex yet uniform mat.  We did what ‘botanizing’ that we could as we climbed: Fritillaria lanceolata, there were Eriogonums, Lupinus, Achillea, Artemisia, with Balsamorhiza deltoidea dominating the expanse, Delphinium and Castilleja spp. peppered it, Dodecatheon sp., Phlox, Phacelia and Lithospermum.  Where the trail carved its route was a broken band, interrupted sometimes by quite a distance, of Taraxacum officinale, the Common Dandelion, the seed fallen from the boots or laces, the pant cuffs, of hikers or from the fur of their dogs.  Many were blooming.

My first inclination, had I had a hori-hori on me, would have been to set to work extracting them.  This would probably be the least disruptive method, creating the least amount of open ground for other weedy interlopers.  Spraying them out, I do still possess my public applicators license for the state of Oregon, not Washington, would create a larger disturbed area and an instant hullabaloo. If we are to work in an adaptive management mode we would do neither immediately.  Taraxacum officinale, is not considered an invasive or an eco-system disruptor here…it is an opportunist.  The invasives are the plants we need to act quickly on.  We all know Dandelion can be problematic in our lawns, which are an extremely unstable, monoculture, susceptible to all kinds of weed invasion.  This meadow is not a lawn.  It is a complex and dynamic mix of grasses, their relatives and broadleaf forbs.  Each one functions in relationship to the rest.  The only ‘open’ ground is the trail and its edges.  It is possible that Dandelion seed, wafting on the breeze or driven by gorge winds, can find a suitable niche here or along its edges.  From the trail we saw no evidence of its successful incursion, though, granted the widely spread Balsam was blooming in all of its golden glory making it more difficult to spot the errant blooming plant.  Still….

It is vital that we know that there is a problem before we work to solve it and that our actions be correct.  This requires monitoring, some kind of visual examination.  If we were to walk the meadow in a methodical pattern, or even to study sample areas, we would be inflicting damage to it directly and could be opening ourselves up to even more damage should hikers decide to explore our new paths.  ‘First do no harm’.  The cautionary principle should apply here.  This said, given today’s technology we could overfly the meadow with a camera equipped drone.  True you won’t see everything.

The cautionary principle would also have us look deeper to the ’cause’ of the disturbance, the trail itself and its use by us, those who come to enjoy the place.  But, trails, have always been a fact of human life and though none of us may ‘need’ to get to the top of Dog Mountain we are drawn to it as humans.  Because of this and our numbers, trails are needed as is the necessary maintenance to preserve the reasons that we go there.  There will never be the political support to simply exclude ‘us’ from sensitive natural areas like this…. All natural areas, in this sense, are sensitive to heavy human use and the invasion of ‘exotics’. Each particular area, will be subject to invasion by a host of plants and animal species. We, as responsible stewards of our landscapes, are in the position of ameliorating our own negative impacts to protect the value of these places.  As a place degrades, it moves out of its historic patterns of dynamic stability and more subject to ‘failure’, requiring more energy and resources from us to stave off its collapse.

The main goal of care takers of a landscape should always be to minimize damage, to permit the dynamic forces and cycles which work to maintain it, removing the occasional invasive before it can spread and compromise the whole system, stopping the human practices which lead to disruption.  Dog Mountain, like other such relatively intact natural areas, especially those near urban metropolitan centers, comes under heavy use during wildflower season.  Trail maintenance, signage and amenities, including benches, tables, even fencing to limit the spread of incidental damage caused by picnickers and their blankets, would help.  I think you would even have to consider some kind of surface treatment on defined areas to minimize mud and erosion.  Meadows such as this can’t tolerate very much foot traffic at all and the further degradation of conditions will allow more weeds to move in and apply pressure to the intact portions of the meadow.

It may likely be that given that there are millions of acres of such natural areas under human pressure, that even in these places there needs to be some tolerance for non-invasive weeds.  In any event it is always more effective to prevent damage whether through law, education or thoughtful design than to wage an unwinnable war.  We must always be asking ourselves, ‘what is going on here’.  This is even more true in the urban setting.

In the urban landscape, given that the expected relationships of the native landscape are absent, maintenance and adaptive management become much more complex.  Like Dog Mountain, we still must address the ongoing issue of our human presence and our impacts on the landscape and that of literally thousands of ‘exotic’ species, a significant number of which can be weedy in certain landscapes and a handful of which are truly invasive and can come to dominate our landscapes.  The difference in the urban setting is that our history, or use of the landscape, its modification, is massive and accumulative.  What remnants have survived are under severe pressure by the vast bulk of disturbed landscapes that engulf them.

Riverplace Esplanade: the urban contrived landscape

Riverplace looking south from the overlook adjacent to the Riverplace Hotel towards the buildings of the Strand.

Riverplace looking south from the overlook adjacent to the Riverplace Hotel towards the buildings of the Strand.

I’ll begin with an example from my own experience here in Portland. It will not be exhaustive, far from it, but it should be illustrative. Riverplace Esplanade, the narrow band of river bank between Waterfront Park’s bowl and the Garden at South Waterfront, is built on created land, fill, graded for the urban purpose of building upon and engineered to help contain the Willamette to a ‘channel’ much narrower than the one that predated the arrival of white Europeans. This combined with the channelization of that portion of the Willamette that wends its way north across the rich bottomlands of the Valley floor and the flood control damns on many of its tributaries has forever changed the hydrology of the river and the nature of the plantings on its banks and within its now dry floodplains. The notion of coming in with riparian plants and expecting them to magically take hold is both naïve and narcissistic. The banks in question are steep and made up of compacted mineral fill soils brought in as waste soils from various construction sites. The biology and chemistry of the soils on this site share little with what was once here. This was marshy floodplain some feet lower than the present grades. The soil flora and fauna work together independently and in synergistic ways to affect directly the growing conditions in a very particular way across it and up and down the bank.

The plants that once grew below our feet here have no natural right to this radically disturbed and created site. It is possible they included the native Cornus stolonifera and Spiarea douglasiana that volunteer here and there and may, if left alone, come to dominate the site…for awhile, but they are unable to hold there own against invasives like Ivy, Blackberry, a couple different Vetch and annual Bromes. Willows regularly attempt to take a foothold along with Black Cottonwood, Red Alder and a host of non-native trees moving in the river’s flow. The river’s edge lacks a tree canopy element across most of it surface. This lack of tree cover was part of the design and was intentional.  Many of the neighbors demanded it.  This ‘fact’, along with the narrowness of the landscape pressed between the River and the high valued built landscape, are powerful factors in what can happen here.  Of course, politics can always change.

This landscape was first planted in the mid 1980’s with Taxodium distichum, in five scattered small groupings, a choice that might seem on first look as reasonable, as it is a bayou native and quite happy with seasonal inundation, but this site has been submerged only once in the last 30 years that I know of. This bank is steep with an easterly aspect and generally bakes during our dry summers. At one time irrigated, it hasn’t been regularly in years, and while showing stress the Bald Cypress are still doing surprisingly well. (They are subject to regular wind damage and one lost its entire top in November ’14’s wind storm.)

The dominant ground level planting was Hedera hibernica, once thought to be English Ivy, roughly an acre of it (43,560 sq ft). By the early ‘00’s it was rapidly moving into its mature phase, flowering and fruiting where it heaped up on itself without the opportunity to scale trees. The remaining planting was limited to Cornus stolonifera, Mahonia aquifolium, Spiarea douglasiana and a little Gaultheria shallon, the usual native suspects.

This was replanted around ’04 with a simple pattern of large, mostly single species sweeps, extending from the top of the bank down to the armored, rip-rap, portion, which was placed as high as the average ten year storm (?) mark as determined by the Army Corps of Engineers. This planting was intend to mimic the effect created by the ’97 plantings, done by Walker Macy, along the bank in the adjacent South Waterfront Park. There was considerable debate during design with minimal concessions made to the native plant proponents at BES, who partially funded the project. The structure and simplicity of the design was held fast by the designing LAs, again, Walker Macy. It was a compromise design that I don’t think anyone was happy with including the adjacent property owners.

[For those interested here is a link to a pdf of the Walker Macy plan that was installed.  It shows the simplicity of the planted sweeps.  The reader can zoom in to better see the details and to read the text.  Riverplace Planting Plan]

The prep for this large replanting project was minimal. The English Ivy was sprayed utilizing a methodology that had been proven effective in the past. A couple of months after spraying, once the contractor was confident that the Ivy was dead (It can be many months before the plants actually desiccate to the point where death is obvious.), trac-hoes and dump trucks were brought in to scrape off and haul away the heavy Ivy mat of vines that had built up on the surface. This scarified the surface soil, but did not penetrate very deeply. There was more concern at this stage for minimizing surface erosion than for breaking up the soil to improve root penetration of the subsequent planting.

Planting was accomplished using power augers to punch holes into the dense soil. It was then planted and mulched with bark. An irrigation system had been installed for the establishment period and probably ran for three years.

I took over maintenance at the beginning of the third growing season. If you’re observant, maintenance shows you how successful your design was. There is a ‘honeymoon’ period with every landscape, the span of which varies broadly, depending on the history, the soil seed bank, on the site and the prep. There is a pattern that new landscapes follow, being relatively weed free at the beginning, again, depending on the seeds and propagules in the seed bank, that progressively develop a more diverse and dense weed population. New weeds arrive at a variable rate depending on the population in neighboring properties, adjacent corridors such as highways, railroads and rivers that serve to carry seed, the amount of seed contaminate in materials you bring in along with plant material, soil and mulch. Users also carry in seed whether in the laces of their shoes or pants cuffs or in the fur of their pets. Seeds arrive one way or another and it is part of the maintenance staff’s job to do what they can to limit this importation and the consequent establishment of a seed producing population on site. The maintenance staff/gardener is in the best position to assess this problem and to act on it. There is a limiting factor that can work to the gardener’s advantage that comes into play with the design and any editing that the gardener engages in.

Landscape and garden maintenance is not simply a matter of keeping to a rote schedule. If the maintenance staff is fully engaged in their work they are continually monitoring and making assessments, evaluations of how the landscape is doing and how it is responding to their efforts. It is an evolving process. What is planted and allowed to grow, in a sense, produces a protective cover for the soil. A well planted landscape is better able to ‘defend’ itself against the incursion of an area’s more common weeds by filling the available niches.  This does not hold true for invasives, which are after all, invasive. We’ve all heard that bare soil is like a vacuum…something will fill it, but with landscapes it’s a little more complicated.

So what constitutes a well planted landscape? The designer or the engaged gardener, must look more deeply into their site analysis. It is not just a matter of USDA hardiness zone and soil type. All the forces and elements at play on a sit are important. Here in Portland, like anyplace, we have to look at the historical landscape, what kind of plant communities occupied this particular type of location? Mixed woodland, Oak Savanna, Riverine flood plain, Rocky outcropping? There is a community type that lends itself to every location. One of the problems we face is that in urban situations this ‘location type’ may never have occurred here before our massive disturbance of the landscape…still there are cues here for us.

If we look to steeper naturally occurring banks along the Willamette, we do not see the almost ‘pastoral’ landscape that was installed at Riverplace or South Waterfront, banks that are seldom or never inudated, that are more parched in our droughty summers. These landscapes respond to the climate, soils, aspect and particular conditions that are extant. They are mixed with tree canopy, a shrub layer, mixed forbs and grasses. Trees like Garry Oak and even Madrone are more likely than the more thirsty Oregon Ash and Red Alder. Down below the high water mark is a more typically riparian community, but on this site, this area is rip-rapped and for years was managed to be clean of plants as the river was seen as more of a drainage conduit than a living river. But as I said there are cues all around us and this will require a certain amount of trial and error.

If one is looking for a model in nature we should probably look to those cliff areas adjacent to the Willamette such as across from Elk Rock Island, but these too are disturbed across much of their surface.  Other examples exist in a more intact state such as down in the Buena Vista area at one of the Willamette’s last ferry crossings near where the Santiam River joins in.  The built urban environment mimics the conditions created where the eroded basalt crowds the river.  Soils tend to be shallow with bedrock close to the surface, unlike the deep compacted fill that comprises the soil here. Drainage is quicker down through the fractured basalt.  Trees and shrubs dominate the slopes where they can get a foothold.  The climate and aspect are very similar.  No native site will present identical conditions.  (Some local professionals working in ecological restoration in their search for naturally occurring models for our most severe urban landscapes, those dominated by concrete, various hard-surfaces and mineral soils have considered the ecology of ‘balds’, those natural basalt outcroppings that occur sporadically in various landscapes across the NW.)  These areas are largely populated by species highly tolerant of drought and the baking heat typical to such exposed areas in the PNW.

If we are to follow our model as described above, we need to define the Desired Future Conditions that our site assessment is most supportive of.  Our desire to plant and maintain a landscape that is consistent with another one in the area, the degrading landscape on the banks of South Waterfront, is wrong-headed and doomed to failure.  These balds that occur in the Willamette Valley and the Columbia River Gorge suggest a different idea, as does the landscape at Buena Vista.  Once chosen we can move on to the next stages of the process.

This is why, as part of my own process, I began to add upland Oaks to the banks including: our native Garry White Oak, Quercus chrysolepsis, the Canyon Live Oak, from the southern portion of our state and Q. wisleznii, the California Interior Live Oak and more, almost all of which have done well except for the setbacks caused by munching Beaver. It should be obvious to all that a canopy layer is necessary here. Below the high water mark I have planted no trees, in part because of the difficulty of planting through the rip-rap, but trees are volunteering in these areas. Red Alder, various Salix, Black Cottonwood and a wide array of weedy interlopers. The ‘interlopers’ I have been ‘managing’ strictly while also controlling the Cottonwood as the City has targeted it as undesirable within the City, while enforcing a milder solution for the willows and Red Alder, leaving them in place low on the bank where they shouldn’t ‘interfere as much with views, which are a City priority, or create too congested or tangled of a landscape making maintenace nigh impossible. The weedy interlopers are dealt with immediately and severly.

While all of this is going on Redtwig Dogwood and Douglas Spiarea are given the selective treatment so as not to congest site lines. Most of these have been left below the high water line. Above this they are selectively controlled to give the more drought tolerant selections I’ve experimented with a chance to prove themselves: Arctostaphylos spp., Ceanothus spp., Rhamnus spp., Holodiscus, Cistus spp., Ribes, Mahonia etc. Many of these have been doing well and I think it will be interesting to see how they do over time and whether they might even establish a more ‘permanent’ population.

A new invader here, Geranium lucidum, spreading fast! Cat's Ear and a little bit of the Achillea that I planted.

A new invader here, Geranium lucidum, spreading fast! Cat’s Ear and a little bit of the Achillea that I planted.

The ground layer that was part of the replanting project was, as stated before, very simplistic. The grasses were all bunchers and covered a large portion of the landscape, the ornamental grasses used throughout the industry are overwhelmingly bunchers. Now there is nothing wrong with these, but their habit is to leave bare spaces around them and this is itself a problem because it provides niches for many invaders. Think of the meadow on Dog Mountain.  These do not constitute a community. As time went by it become very obvious that the bunch grasses and the very few perennial forbs, that were included, would not grow into a protective mat. These areas came under heavy attack by the weedy Cat’s Ear and the many annual and perennial weeds that plague this area. Maintaining this out of balance contrived landscape quickly became impossible. I could not keep up with it given the limited manpower available to me. I found myself ‘forced’ to use herbicides. Herbicides are a two edged and blunt sword. They damage the non-target plants as it is all but impossible to spray with the kind of precision needed. Herbicides are ideally suited to the management of non-sustainable landscapes, where the desirable plants are surrounded by a buffer of bare soil. In a landscape where you are trying to move the plantings to a more sustainable, balanced and blended community of plants, herbicides are too indiscriminate and will prevent you from moving toward your goal.

A couple of years in I began planting more broadleaf plants to create a better ‘mat’ that would be more resistent to invasion. At the same time I broadcast Creeping Red Fescue, Festuca rubra var. commutata, to help fill in the spaces between the bunch grasses. Meadow communities always include a mix of bunch and spreading grasses and forbes. The original planting left too many opportunities for invaders to gain access. Once in, as prodigious seeders they were in a superior position to dominate the site. My maintenance practices, along with the original design and the weed pressure exerted by the seed bank and the adjacent corridors, virtually assured that the landscape would decline.

This coarsely filled and steeply graded bank is facing Riverplace from the east side. It is filled with rubble and populated almost entirely by 'weeds' several of which are invasive. This portion of the bank was historically marsh and slough even beyond MLK blvd which was originally built on pilings. This is part of the same river landscape and is characteristic of much of the channelized Willamette lying upstream from, and therefore impactful of, the Riverplace site. Such landscapes were unimportant as they occurred at the 'edges' and were incidental. The weed species available was much more limited at the time and there appearance probably tended to be more bare as the native and newly arrive weeds were not well suited to invading it.

This coarsely filled and steeply graded bank is facing Riverplace from the east side. It is filled with rubble and populated almost entirely by ‘weeds’ several of which are invasive. This portion of the bank was historically marsh and slough even beyond MLK blvd which was originally built on pilings. This is part of the same river landscape and is characteristic of much of the channelized Willamette lying upstream, and therefore impactful of, the Riverplace site. Such landscapes were unimportant at the time of their creation and were not considered as such, as they occurred at the ‘edges’ and were incidental to their creators purpose of creating developable land. The weed species available were much more limited at the time and the appearance of these banks  probably tended to be more bare as both native species and newly arrived weeds were not so numerous nor well suited to invading it.

Other plants also began to move in on their own from populations upstream, notably, Juncus effusus, or Soft Rush.  Interestingly these began appearing both above and below the average high water line, often into areas that saw no inundation in the 17 years I was responsible for the area.  While Juncus patens is preferred by those doing restoration work, as it is less aggressive, here, on this more difficult site, I chose to leave it.  Usually, what came down the river was weeds, e.g., Purple Loosestrife, Iris pseudoacorus and their ilk, invasive highly problematic weeds.

For a few years I attempted to hold the line at the ground level, but I never seemed to gain headway. If I used a non-selective herbicide, wherever I squirted it, left a dead spot, larger than the plant I was trying to remove. This new dead zone was prime for the reinvasion of the most aggressive plant available, almost always weeds, a result that can be counted on. While spraying with a more selective broadleaf spray, attempting to control the pernicious Vetch, Canada Thistle and Cat’s Ear growing in and among the grasses, I occasionally doomed one of the native Asters, Achillea or other forbes I was trying to establish. No matter how careful I was, I would hit some of the more desirable plants and, because they are much less prolific, my efforts were contributing to the decline of the very plants I was trying to increase.

The nail in the coffin, that finally destroyed any shred of hope I had of gaining an upper hand with this strategy, was the arrival a couple different annual Brome grasses. These made all of the other weeds appear bashful by comparison. I finally became convinced that the only possible way out of this was to do what I could to limit seeding on site and to do everything I could think of to improve the vigor of the plant community I was trying to build.

Every Brome plant I pulled disrupted the soil. Every plant I sprayed prepared the way for more weeds. So I quit pulling as a general practice opting to cut and squirt weeds like Blackberry, a time consuming but much more targeted tactic. I greatly limited the use of non-selective herbicides and reduced my use of broadleaf sprays. Instead, my goal was to weaken the weeds and stop seed production, there were exceptions for some of the worst perennial weeds, by mechanically cutting annual weeds like the Brome or spraying, which was quicker and less physically wearing, with a contact herbicide based on fatty acids (soaps). While this would cause damage to some adjacent perennial desirable plants they would be able to spring back from it.

The idea is then to increase the tree canopy, build and diversify the brush layer and continue to diversify the ground layer minimizing the heavy hand of herbicide use. As plants are added or arrive on their own, the maintenance staff needs to continue this evaluation process. Are there any holes I can fill given regional examples? Should I modify my practice? Are my efforts contributing to the problem? If I leave this alone, is it reasonable to expect the problem to resolve itself. Is my action necessary? Do I need to shift the plant population by adding more evergreens? Is there a plant I can add that can tilt the advantage away from the Brome? Will the canopy reduce my problem? Will time help simply by allowing soil chemistry/biology to adjust over as desirable plants mature? Can this community continue on its own? Is there a plant that can better fill the niche, that can establish a longer term resident population that replenishes itself?

Tanner Springs and The Fields – Urban Extremes, Brownfields and Contaminated Groundwater

As bad as conditions may be at Riverplace Esplanade they may be worse at landscapes capping Brownfield sites that pose a threat to contaminate groundwater.  Many of these are abandoned or redeveloping industrial sites and so have minimal slopes and by law are hard-capped to prevent percolation down through the soil profile and the consequent movement of groundwater off of site.  They are generally topped with 1 1/2′ to 2′ of topsoil.  Essentially, we are required to create perched water-tables on these sites, that unless your are trying to create a bog garden, is something we try to avoid.  During our rain season from October, through as late as the end of June some years, this top layer can present anaerobic, unhealthy, soil conditions that most landscapes will struggle in.  This can result in similar conditions throughout the summer if supplemental irrigation is not carefully monitored and matched to evapotranspiration rates.  This, effectively, greatly reduces the rooting depth of plants leading to possible root rot, poor anchorage and toppling of trees and, counter intuitively, to summer drought damage because the healthy roots are limited to the top layer of the soil which is most subject drying out.  This creates a vicious circle.

Drainage is problematic on these sites.  Surface drainage is very slow due to the limited slope.  Water moving down through the soil profile is interrupted and simply sits because the slope of the hardened cap is also minimal and the cohesive/adhesive forces between the water molecules and with soil particles further inhibits its movement ‘sideways’.  Drainage systems, when installed, are never ‘perfect’ only removing a portion of rainfall, and, if they’re absent as they are in all of the bed areas at Tanner Springs, then….  Temperatures and plant growth during the cool rainy season combine to create minimal evapotranspiration, so there is little ‘pumping’ effect to remove water from the soil.  I have dug in both of these sites, Tanner Springs and The Fields, and typically they are saturated during the rainy season, which means flooded pore space between soil particles, forcing out air which is necessary for the health and growth of most plants.  Both sites regularly lost plants due to root rot/ water logging, The Fields still is.

Once we took over maintenance of Tanner Springs, after a three year maintenance contract expired, we immediately shut down all but the turf irrigations zones, reducing the summer saturation problem.  The original upland plantings were largely native and should not have needed any supplemental water after establishment, but the contractor was nervous and kept them on.  I began to add to the drought tolerant plantings in the Tanner Springs upper beds including native Iris, Arctostaphylos, Zauschneria, Sidalcea, Carex tumulicola, Philadelphus lewisii and Amelanchier in an attempt to fill some of the empty niches. This site is still very much in process.

The lower portion of the Park, has a created soil installed that no one has yet figured out how to plant.  The original wetland plants, planted repeatedly, succumbed.  The droughty west coast natives, many from California, have been only marginal performers.  It is an ongoing problem.  Why were we trying xeric west coast natives in a wetland?  This lower, portion of the Park, was intend to cycle the water from the pond, which is collected in part from drainage off of the surround Park hard surfaces aiding in cleaning it.  This whole area, the ‘wetland’ and the pond are installed over concrete, that creates a large, unseen tub.  The pond is underlaid with fist sized and larger, round, river rock, instantly penetrated by the pond water.  Plantings ‘in’ it were made into individual pots.  The ‘wetland’ ‘soil’ is a very specific fine pebble mix, that too could be easily penetrated.  There were other components in this mix, the end result of which was supposed to be capable of ‘wicking’, through capillary action, the pond water up into the roots of the above planted wetland plants.  To aid in the filtering process, a pump was installed that was to speed the movement of the water through this soil that was then released at a ‘spring’ in the upland portion allowing it to return to the pond via a series of little streams.  The whole system required some pretty major tweaks to work at all.  More ‘stream’ channels were added to spread out the surface wetted area in hopes that that would be enough to support the wetland plants.  They were planted several times.  Annuals and short-lived native perennials were attempted over seeded in the dormant season.  Most of these attempts never took.  The most successful were the plantings along the pond edge and in and next to the little streams, where these could get adequate water.  Over time, as the rock lining the pond bottom began to silt in, as ponds will, Bull Rushes, Cat-tails and Water Lilies began to root in and spread.  This too was not part of the original plan as this sedimentation would slow the movement of water through the installed soil matrix.  The pond was to have been routinely ‘cleaned’.  Neighborhood politics intervened.  Modifications had to be made to the pump system as to keep it functioning.  Such are the risks with experimentation and trying new techniques and strategies in pursuit of an admirable goal.  The end result was that the original plant palettes used had to be rethought.

The Fields in NW Portland, a brownfield site, strictly controlled by DEQ. The grass field has a drainage system. Much of the Park has saturated soils throughout much of the year

The Fields in NW Portland, a brownfield site, strictly controlled by DEQ. The grass field has a drainage system. Much of the Park has saturated soils throughout much of the year

Tanner Springs and The Fields were recognized from the beginning as non-native urban landscapes.  Planners assumed that the added topsoil and the planned drainage systems would remedy any drainage problem, and they were planted as if there was not one.  This is the perfect opportunity to implement an Adaptive Management approach.  These will never evolve into a pure native state of history.  They could be moved toward a more sustainable condition in which our participation/ intervention, in the form of maintenance, is greatly lessened, but egos need to be set aside and a creative, thoughtful approach taken.  Given the conditions and the legal requirements that prevent a more thorough preparation of the site, the Desired Future Conditions must be changed to reflect the limitations presented on these sites .  The current Prescription is unrealistic and will result in an endless series of Interventions, replanting projects and a never abating weed problem.   Landscapes like these are doomed to fail.  Are there any models out there in nature we can look to?  Perched wet areas that dry out and bake in summer?  Surely there must be.  The steep bank along the arcing northeast side adjacent to the railroad tracks at The Fields could support a landscape similar to the one I began at Riverplace on the bank.  Granted, as Parks, we need these spaces to fulfill certain social needs for open and/or active space, but they needn’t be such a burden on our resources.  We must adjust our expectations and those of the public and practice good horticulture.  That’s what this is ultimately about, being sensitive to a site, adjusting our response to it and changing the aesthetic that compels us to blunder ahead in spite of everything around us.

Whatever the landscape or garden which is ours to maintain, these same questions confront us. We are a part of these places. We are not just outside actors. The fact that our gardens are massively altered from their natural state does not change this. That their history was altered by  predecessors, not necessarily ourselves, does not give us a free pass. That the original communities are wiped away entirely does not mean that the cycles and forces that once determined these places no longer apply. What this means is that it is now upon us to create and foster the development of new communities, communities that tend to be mutually supportive, which possess a resilience capable of returning them back to a ‘center’ point, which is itself, refining and evolving over time, becoming more robust in the process. Such communities require our participation. Just as we chose to ignore these cycles and communities before, now we must search for what was lost and use our knowledge and energy to marshall and support something new and ‘healthy’ to take its place. Health is what we have sacrificed in our places. We refused our role in its processes and had the arrogance to believe that health didn’t matter. That we could instead marshall our own as well as the energies and resources of whatever places we chose to created our own aesthetic and that health, would not exact its own price from us. But health is central to any living system and when we sacrifice it we incur a debt. Taken too far, we may not be able to repay it, especially when we do not understand what it was that was lost. Adaptive management is a method whereby we are able to ‘play’ within the limits of a living system, without incurring  unmanageable debt. In the economy of the living we do not get to set what something is worth. In a money economy, which is itself  a human invention, an abstraction, we can play such a game, but living organisms and the systems that they all comprise, are not abstractions. Treating them as such greatly increases the odds that we will lose something we can ill afford.

Adaptive Management is a tool, a method, that if wielded adeptly can begin to get us out of the hole we are now finding ourselves in.  It recognizes that there is an energy, a rightness, in a healthy functioning organisms and systems that is self-correcting. That if we do so that it can lead us back toward health. The world is not infinitely adaptable.  We cannot mold it into anything we want.  Our human landscapes and gardens are interconnected with the larger and more complex world. It is in the nature of living dynamic systems to, as they regain their health, their robustness, that they will begin to heal and connect the various disparate parts we have broken and separated. The energy conducted through a dynamic and health system has a particular capacity to self-right and will tend to engage other interconnected systems in a similar healthy manner. There is a literal ‘harmoniousness’ which exists between integrated organisms and systems. If we want to continue this human experiment, we will need to better understand the complexities that are essential to the healthy functioning of a habitable Earth.  We have been changing the world…rapidly. There are no do overs.  Adaptive Management offers an alternative view and path for us to follow. It is a way of living with the world we find ourselves in.  It requires us to be thoughtful and to temper our actions while at the same time it reminds us that we are responsible, ultimately, for what happens here.


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