The world is finally, at the last minute, waking up to the impending effects and consequences of climate change. In the scramble to work out we must do (apart from the obvious cessation of burning fossil fuels), one thing, one factor is looming large: we need to put carbon back into the soil, where it can be stored indefinitely, and we need to reforest the Earth. Much of this is in the agricultural realm but there is a huge amount that can – and must – be done within the landscape and horticultural sectors.
Horticulture has a MISSION, it just doesn’t realise it yet
At the centre of this is good soil husbandry, something that we have largely forgotten about. Modern agriculture bypasses all need of soil health by chemically feeding crops; no need for microbes, nutrients, humus, mycelium or earthworms. Chemical fertilisers and herbicides bypass the lot. Most of our soils now are depleted to the point of useless by chemical farming, exacerbated by the tradition of ploughing, which causes erosion from rain and enables much of the soil carbon to move back into the atmosphere.
So whilst we need current global models of food production to transform into regenerative agriculture and agroforestry, we also need to look at our urban landscapes and gardens, and create a new design ethic, a new paradigm, even. I can’t deal here with agriculture but I have been thinking long and hard on what the landscape and horticulture trades need to do; fortunately, I believe there is a lot that we can do.
We need to envelope our existing horticulture trade within ecology, to create an “environmental horticulture” You could also call it ecological, resilience or regenerative horticulture. We (those of us in the trade) know that as a profession, the training of both horticulture (growing) and landscape (doing) are in decline. Horticultural colleges have shrinking budgets and often get the less ambitious or capable students; after all, who is inspired by the prospect of strimming verges or hedge-trimming another unloved carparking lot? Yet last year’s report by the Ornamental Horticulture Roundtable Group valued horticulture at £24.2 billion in GDP in 2017. That’s not inconsequential, yet it goes unrecognised. Fortunately, there is a way to make it much more enticing to prospective students.
Horticulture has a MISSION, it just doesn’t realise it yet. That mission is to adapt our urban landscapes and gardens to cope with climate change, to mitigate temperatures, water flows, to grow biomass and regenerate soils back to health. Healthy soil is the foundation of life, of all life, including our own. Good soil holds fertility, water and carbon. Yet who amongst us now knows much of soil science? Who designs landscapes as ecologies, as “novel ecosystems”, who chooses plants because they have these abilities, not just for pretty flowers? Who designs plantings for their biomass harvest, for creating mulches to feed the soil?
In this respect, I don’t believe it’s necessary – or right, in fact – to work with native plants only. What is native? What was native? What was here 11,700 years ago when the last glacial period ended and the glaciers retreated? Flora and fauna move around the globe all the time, they are opportunistic, not fixed permanently into some tightly integrated ecosystem. We know there is no “ecological climax”, no ultimate ecosystem for any given place. As temperatures rise, climate zones are now shifting away from the equator quicker than Nature can keep up, although it’ll get there eventually. Maybe we help nature, rather than interfere when we bring in exotic plants that naturalise. Maybe those plants are the start of new ecologies that will adapt to the rapid changes that this climate emergency is bringing us. If plants do well, we need to understand how to enhance and build new ecologies with them. This is how we adapt, how we survive and how we rectify the damage we have done as a species; not by returning to some pristine “before” (which doesn’t exist) but by assisting Nature to heal and adapt. The Earth will do this all by itself, and has done so many times. It doesn’t mind if it takes thousands, or even hundreds of thousands of years to adapt. But we do; we can’t wait that long.
So horticulture needs to stop growing pansies in peat with unrecyclable plastic trays and start sorting out which plants really matter for our future; which ones contribute to new and existing ecologies, which ones are good for biomass, which ones contribute to soil health, which ones give us ecosystem services. We should not enhance one environment at the expense of another.
That’s a very-near future profession of trained eco-warriors, soil saviours, tree patriots and landscape lovers. It needs people who understand soil, who know how to design and use sensors, data and the internet of things, people who see what’s coming and how to mitigate and reverse negative effects, people who really know how to design and install green infrastructure and future automated robotic maintenance systems. Our landscapes can grow food in amongst all the beauty, with urban food forests. We need new knowledge built on old and we need passion, commitment. A wise government would fund this for the returns will be numerous.
This is the enlightenment, that out of dire stress and trouble, we could really learn how to value, connect with and protect this crazy, beautiful world within which we live. Or we can do nothing and watch it all go to hell. I know which I’ll be doing.
A problem, or an opportunity for a new landscape paradigm?
I was recently working on a tree project in Abu Dhabi when I came across a derelict site which intrigued me with it’s range of exotic self-seeded, non-native plants. The site was next to the Corniche and sandwiched between the Formal Park, my hotel and Capital Gardens. It struck me initially as the perfect basis of a xeriscape, as all the plants (mostly trees) were thriving without irrigation. On closer inspection and identification of the species involved, things got more complex and raised a lot of potentially conflicting thoughts and issues.
A natural Xeriscape
The site was clearly awaiting redevelopment and the plant invasion was opportunistic. Nothing that I could identify was native, yet all seemed happy there. When you see the list, you might understand why. Amongst the plastic and litter I identified:
Of those plants, the P. juliflora was the most robust and when you look at its reputation, that is of no surprise. It was of landscape scale, lush and greener than anything in the adjacent parks. It’s form, leaf, flowers and seeds are attractive from a landscape perspective. Yet this is undoubtedly the most controversial plant on this list – some would say alarming. A Native of arid zones in central and South America, this was, like so many others, introduced into the UAE in the 70’s as a forestry plant. Lauded as something of a super-crop tree, it is tenacious, vigorous, provids fuelwood and stock-feed in the form of abundant seeds. The latter, it turned out, were a problem in that they are spread by cattle and are extremely aggressive. Plants also regenerate rapidly from the roots when cut back and they reputedly produce biochemical inhibitors to suppress competition (allelopathy). With no natural competitors in the UAE and roots that can descend 50m in search of water, they out-compete native flora, even their cousin, Prosopis cineraria (ghaf tree).
Prosopis juliflora flowers
P. juliflora has a low, mounding habit, attractive from a landscape point of view.
Also on the site were a number of Banyan trees, Ficus benghalensis, which seemed to be growing happily. Another tough survivor, it should be borne in mind that the water table here is likely only a metre or so below ground, although it will have a high saline content.
Then there was Eucalyptus glaucescens, another forestry/amenity introduction of the 70’s, also known and now generally avoided for its aggressive roots, yet here looking beautiful with its grey, lanceolate foliage. This was the tallest tree on site.
Eucalyptus glaucescens, showing adult foliage
Of course, there was the ubiquitous Conocarpus lancifolius, widely planted still yet also recognised and a danger to any nearby drains, and on it’s way out in popular use. Except it does make such a good tall hedge, and it has a much nearer native origin, coming from Somalia, Djibouti and Yemen. I’m not sure that the UAE landscape industry is ready to ditch it just yet.
There was even a palm, Washingtonia robusta, self-seeded around the place. Much of it was to be found growing underneath the canopy of the P. juliflora, so that at least is not put off by any allelopathic biochemicals from the Prosopis.
I believe this legume is Sesbania sesban, more commonly seen with yellow flowers. Rose-ringed Parakeet
Inhabiting, or at least visiting the site, was a Rose-winged Parakeet. Another exotic invasive with beautiful form but aggressive tendencies; it seemed appropriate to the moment, somehow.
What does this mean for future landscapes and ecology?
From a conventional ecology point of view, these plants are all threats, and the threats probably outweigh their usefulness. So why am I even talking about this? Clearly, the move towards more naturalistic landscapes draws heavily on native species and would shun all of these species.
Except we have climate change.
Climate change is the elephant in the room, when it comes to ecology, in fact when it comes to sustainability generally and a livable planet overall. That we have already moved beyond vital tipping points is highly likely; that climate zones are moving away from the equator at a rate too fast for nature to adapt is a fact. Flora and even some fauna just can’t move regions that quickly. They will adapt, eventually; but those that are rare, specialist and struggle with change, will die. The tougher generalists will adapt and survive. Nature will build a new ecology to reflect the new reality, and it doesn’t mind if it takes a few thousand years to do so. Only we humans mind and so, if we are to survive, we must adapt our environments to fit the new reality. It is a sad fact that many cherished plants will eventually die out or move zones. In the UK, I dread losing our native oaks (I view these as our ghaf tree equivalent), yet we may get Mediterranean species to replace them, such as holm and cork oak.
If you are already positioned in the arid equatorial zones then you have precious few plants that will form your new ecologies and landscapes. Perhaps the plants I have described above will be UAE naturalized-natives in 100 years’ time and the ghaf and sidr may be gone, or diminished, or moved north. I hope not, but before we spend vast fortunes on eradication and control of non-natives, we should look to the future. These aggressive invaders may just form the landscape of our children; I know I’d rather live with a landscape, than none at all. If there is no landscape, there is no life. They may, in fact, be here to save us.
Once we grasp this fact, we can look at building new landscapes to suit our changing environments. I’ve written about this before and you can read the articles listed below. We must be vastly more holistic in our thinking in order to do this and broaden our horizons to understand the new future. Technology will help us to monitor, collect data and produce working strategies. Robotics and drones will help manage and control plant communities. Alongside that, we need a vastly better understanding of soils, microflora and fauna, for the bit of nature that we see is just, literally, the tip of the iceberg. The selection of tree and shrub species for adaptation is easy, we get this wrong when we don’t deal in whole context thinking eg. only thinking of forestry or ornamental benefits.
The challenge ahead is huge but in a weird way, exciting; it will challenge the human race to grow. There’s a whole new science to develop and we’d best get on with it.
I’m pleased to have launched a new website and blog dedicated to this aspect of my work. Over time the blog will become a useful resource to all those interested in the care of trees in the Middle-East. My focus and experience has so far been within the UAE but the tree range is similar in most GCC countries. treecare UAE
On my most recent trip to Dubai, I enjoyed walking through some of the new landscapes that emerge as projects are completed. The UAE, along with most regions of the Middle-east has a rather limited palette of plants to work with (although that is growing as new plants are tried). What struck me, however, was how poor the quality of nursery stock was in some cases and what problems are being created for later, especially with regards trees.
This is not new, nor confined to this part of the world but it bothers me that new areas of urban green are sometimes given a poor start with sub-standard nursery stock, often flown in from other parts of the world.
Simple pruning at an early stage would have improved this tree’s framework, removing crossing and rubbing branches.
Wandering around a residential area in Jumeirah, I came across some newly planted Delonix regia, one of my favourite exotic trees. At first glance it looked nice, a simple planting of trees and groundcover but on closer inspection I was somewhat dismayed at the condition of the them. The problems of poor framework were caused by their time in the nursery, not due to planting, although some of them could have been rectified by a vigilant planting crew.
This tree tie – complete with post – must have been like this from the nursery. The post did not reach the ground.
Many of the dozen or so trees had ties left on which the tree had grown around completely, making them impossible to remove. As the planting is only around two years old (by my estimation), these may have been on the trees from their time in the nursery. Possibly the planting was older and pre-dated the building they were attached to and the trees then grew around the ties after planting. Either way, it’s a strong indication of neglect or lack of care. In the picture below, all the bark ridge above the tie may indicate “included bark” – bark sandwiched against bark, preventing live tissue growth and a strong branch collar formation.
The tree tie is trapped with “included bark” at the branch collar, which indicates a potentially weak branch join.
Several problems are arising here: pre-planting care in the form of correct formative pruning (five minutes with a pair of secateurs) and Post-planting care in terms of releasing planting ties – if they were not simply left over from the nursery days. If there is no way to go back and release the ties, a bio-degradable tie should have been used.
This Ficus nigra was most likely damaged long before it was planted in this location.
Damage to the main trunk or structural framework of a tree might go unnoticed when the trees are small but cause major problems as the tree gets older and puts on size and weight. This can range from the cosmetic to the potentially dangerous in a large tree and at this stage the remedy is costly and the expertise hard to find.
As fast-growing cities like Dubai mature, the needs of landscape shift from creation (in a hurry) to maintenance (at a constant pace). Skills, awareness of the need for – and absence – of skills, will become more and more urgent. If Dubai wants to keep it’s beautiful, green mantle, then there is a whole new phase of arboricultural care awaiting to be discovered and initiated. I have carried out trees assesments and given basic training of correct pruning methods in the UAE, but that has hardly scratched the surface; there is a lot more to be done.
Trees are the urban, biophilic, blanket that clothe and surround the concrete mountains we build. Trees make hot places not just bearable, but unbelievably beautiful. Trees absorb dust, cool the air, add moisture and oxygen and enrich our Souls. We need to honour and look after them, so that they can look after us.
This article first appeared in Pro Landscaper Gulf – a .PDF copy can be seen here on page 12. It is based on tree consultancy work I have undertaken in Abu Dhabi in recent years.
Irrigation is taken as a necessity when landscaping in arid climates. It is a view that I wouldn’t like to completely contradict, yet I have seen a fair bit of evidence that tells me many plantings, and trees especially, are over-watered. Of equal importance is the fact that many of the irrigation methods are wasteful of water and sometimes damaging to the trees themselves.
Lawn Watering with sprinklers is damaging the trunk of this Millingtonia
We have to discern the different needs of trees and understand that what is necessary for one species is overkill for another. I particularly speak of natives verses exotics. Ghaf and Sidr you will see growing wild and without irrigation but imported exotics need a regular supply. I have seen Ghaf blown over in irrigated plantings, caused by shallow rooting from an easy water supply.
Bacterial wetwood in Delonix regia caused by overwatering. It also reduces the flowering, for which these trees are famous.
How the water is put on is just as important; pop-up sprinklers in lawns can damage the trunks of trees, causing aerial rooting in species like palm or fig, discolouring bark and causing stress-induced rots to occur in others. Exotics like the Flame tree (Delonix regia) get over-watered, causing a reduction in flowering and a susceptibility to bacterial wetwood (slime flux). Even drip irrigation is not ideal, as it applies the water at the surface and promotes shallow rooting. Trees with shallow roots are vulnerable to drought and so dependent upon the irrigation supply – a vicious circle.
Excess surface irrigation is wasteful.
In the UK, we are used to putting in a subterranean irrigation ring around trees, which gets water to the tree roots at a deeper level. For watering established trees, perforated tubes can be utilised, inserted vertically throughout the root zone and either manually watered, or connected to standard irrigation systems. Supplying water at a slightly deeper level means less water used and wasted. A word of warning though – most feeding roots occur in the top 300 – 500mm of soil, so watering too deeply can also be wasteful.
Tree roots growing along the line of surface irrigation pipes
In coastal cities, problems can arise from a naturally high-level, saline water table. Halophytes (salt tolerant plants) have evolved to cope with this, but for some imported species, salinity can be a problem. You also have to be aware of the quality of the irrigation water itself, which if drawn from the ground, may have a high saline content. Get your water supply tested if you are unsure.
Ultimately, I believe that planting styles and expectations of “landscape” must change. A more natural style, with more xeriscaping and use of natives or other arid loving plants from different parts of the world (but from similar conditions), will emerge. More important, in my view, than using strictly native species, is building plant communities that function and thrive in place without much human care or maintenance. As climate zones shift rapidly around the world, nature cannot keep up and it will be down to us to create landscapes that sit well in their altered environments, whether native or not. I believe we can do this with considerably less use of irrigation. The water we do use should then be grey water (from taps and sinks), which is a much better way to conserve processed water use.
Canopy of Delonix regia
The goal has to be minimal water use, natural, ecologically benign planting and urban environments which feed our biophilic needs for connection to nature.
Zizyphus spina-christi, crown of thorns tree. A native of the UAE
In my previous post I talked about a regenerative planting methodology for urban landscapes, in which I suggested you would manage, rather than maintain your planting areas. So how exactly do you you do this? Both involve work and the difference is a subtle but important one, in both attitude and application. Think urban forester rather than garden pruner. The picture above illustrates this perfectly, so let me explain.
It shows two hazels in my garden, both planted as young bare-root trees in the winter of 07/08. The one on the left was coppiced down to the ground in the winter of 12/13, the other has been pruned to keep a structure of older wood, with all suckering growth removed annually. What is the difference? The coppiced hazel has been less work overall and has not been touched since it was coppiced, the pruned tree has been pruned annually, which was not great amount of work but this is just one tree. If there were a hundred, it would be a different matter. The main difference is that the pruned tree has catkins, the coppiced tree does not, but I think this is a difference of genetics, rather than pruning technique, as they have always been like that. The shape of the pruned tree is also wider in its spread and will become gnarled as it gets older.
So in terms of management, if you go the coppice route you do nothing much to the trees except coppice them every 4-5 years. I would suggest that 50% of the trees are coppiced so that not all structure is removed at once. Notice that the growth of the coppiced hazel is straighter, making for a productive yield of canes and poles that can be used in the local community. Other trees that can be coppiced include sweet chestnut, lime, alder, ash, willow and hornbeam. Birch and oak will coppice, but from young trees only. Willows and dogwoods grown as bushes for their winter colour can be coppiced or “copparded” (inbetween coppice and pollard) to around 300-600mm every two years to keep the winter stem colours strong.
Salix elaeagnos (foreground)
By adopting such techniques in our larger masses of urban street planting and parks, we would deliver a more biodiverse, beautiful and biophilic interaction for all concerned. It would also cost less both to establish and possibly to maintain, than traditional planting. The above willow is beautiful and graceful, yet I have seen it all too often used in municipal car-parks and reduced to a-n-other shrub that is caressed all to frequently with the indifference of a hedgetrimmer.
Time to re-wild our inner selves, and our urban landscapes. We can do so much better than the average landscape we see in our towns and cities.
Almost all urban landscapes are contrived and designed, due to their artificial nature and short timescales of development and use. We see increasing use of mature rootballed trees and extensive hard landscape and this is normal for intense inner urban areas; I do get concerned that the increasing complexity of urban planting systems divorce trees particularly from their natural functions and prevent the occurrence of the biological interactions/communities that go to make up an ecosystem. For example, I have seen trees planted whose surface levels are around a metre below the surrounding paving level. No matter how well designed, this seems fundamentally wrong to me.
So I’m thinking that there must be a way of dealing with the majority of less intense landscape zones (especially where there isn’t the financial budget that a high-end development attracts) to provide urban regeneration, ecological restoration and biophilic connection, all on a modest budget. This would create a new method to allow for wide-spread adoption in urban and suburban zones. I think the solution comes from Nature’s own process of natural regeneration and a developed philosophy of minimal (but specific) preparation.
silver birch are pioneering species for natural regeneration
Starting from the observation that Nature is very efficient at regenerating itself, what can we do? Too often, I have seen unnecessary interference in this process. I still recall that a few years after the great storm of 1987, I walked through some nearby National Trust woodland of pines and birch. A great deal of damage had been done with many trees blown over. Birch had however, regrown abundantly from dormant seed and was already three or four foot tall. The NT then sent in the bulldozers to clear out the fallen wood so the area could be – replanted. I watched them tracking over all the natural regeneration. Why didn’t they just leave well alone? The restoration of the woodland was only slowed down by such clumsy interference and this was not even a productive forest.
If we simply broke up paving in our urban centres and loosened up the sub-base, what would happen? Nature would soon find a footing and things would start to grow; however, that process would be too slow and unpredictable for human sensibilities. So what if we did a little more, adding a small amount of topsoil to the rubble, planting small (1+1 year transplants) bare root trees and shrubs, with plugs of understory forbs, ferns and grasses. Starting so young, we’d generate a successful community in no time. These could be designed as narrow ribbons – two to four metres wide, inserted into suitable wider areas of paving.
An urban area suitable for natural regeneration
The above area was one I thought would be suitable for such an approach; there are many such areas throughout all urban spaces. They cry out for regeneration, yet seldom can this be done for lack of adequate finance. Below is a quick sketch showing how it might look.
Sketch showing regenerative planting
The benefits of such an approach would be huge. It would cost far less than using a traditional approach to landscaping such an area, maybe half (I haven’t costed it!). The care would move from maintenance to management, using a rotational coppice methodology, rather than trim and tidy (which always ruins a plants natural habit. Biodiversity would be hugely enhanced, air pollution mitigation would increase, wind buffering, urban heat island reduction, stormwater runoff (they would act as rain gardens) and of course, our biophilic needs, our connection to nature.
Last winter I did some interesting work in Abu Dhabi, concerning the care of trees. I can’t name one of the projects (a royal palace), but one was Mushrif Central Park undergoing a major redevelopment (and now reopened – March 2015). In both places I undertook a survey of 100+ broadleaf trees (as opposed to palms), assessed their condition and trained staff in basic arboricultural pruning techniques. Such information is lacking out there as most such trees, with the exception of things like ghaf (Proposis cineraria) and acacia (A. tortilis) are imported from abroad, so knowledge of the necessary arboricultural techniques of pruning, especially of broadleaf trees, is generally absent (palms they are well used to dealing with).
As you can see in the pics, the trees in the park had been “salvaged”, which is perhaps not a good word. A specialist tree-lifting company from the US had been engaged to train ground staff in the techniques of boxing and lifting the trees, no easy task in a pure sand soil and 35-40degC – and that’s the winter temperatures. I then had to attend to the care and aesthetics of the tree. My assessment was that most of the trees had been badly pruned in the past, causing poor crown developments and in some cases allowing disease to enter.
Not surprisingly, some of the trees suffered severe shock in being lifted, but most survived, with varying degrees of die-back and then regrowth. Much of the work was simply about deadwooding and the teaching of correct pruning cuts and methods. Access is always the main issue and there was no way to teach the guys how to climb – that is a job for a specialist training school, so we were restricted to a cherry-picker and for the most part, hand tools.
Many trees suffer, surprisingly perhaps, from over-irrigation. This causes surface rooting which makes trees dependent upon continued irrigation, plus natives like ghaf become prone to wind-throw from lack of deep anchor roots. Exotic trees such as Delonix (below), grown for their beautiful red or yellow flowers, bloom less well when over-watered and become prone to bacterial wetwood infection.
Places like Dubai and Abu Dhabi are developing at an astonishing speed and their landscapes are growing at a similar rate. Knowledge is the thing that lags behind, and it will take some time for this to catch up. I’m sure it will; there is something alluring about creating beautiful landscapes in a naturally hostile climate. This becomes a critical issue in the light of climate change and global urbanization, which is happening fastest in the hotter regions of the world; landscapes moderate climate and make such places livable, whilst biophilia demands that we need close contact with greenery in this urbanised world.
More needs to be done to increase the knowledge and care of trees, including species selection and nursery practice, reducing over-irrigation and teaching good pruning methods, but it can be done. I’m looking forward to the next phase.
I am working as a consulting arborist in the UAE for a couple of large projects. Whilst there, I have been observing the broad state of the art and there is a long way to go in bringing across current best practice to the Middle-East, and I suspect that is so for many parts of the Middle-East and Asia. Even in my village in Sussex, in the last month tree butchery has occurred, so the UK still doesn’t always get it right, despite a long tradition of arboriculture.
I have always worked in accordance with the advise given by Dr. Alex Shigo, of the US Forest Service. His investigations revolutionised our understanding of the way trees react to injury, and this should inform the inquiring arborist. Sadly not everyone inquires.
Delonix trees in a public park in Dubai – note the split branch over a footpath!
Back to trees in the UAE. What I am seeing is a gradual awakening of interest in the care of trees, and the acknowledgement of the skills needed to carry out that work. It seems that as more emphasis is put on landscape and more trees are planted, there comes a point when caring for them becomes a higher priority. This needs to go right across the board, to include the correct pruning in the nursery, this can save many years of bad growth habit, which is not always correctable later. Prevention is always better than cure. Perhaps the UAE, and especially Dubai, is maturing to the point of switching from development to maintenance. That’s as true for arboriculture as it is for plumbing and building maintenance.
A part of my contracted work is to train local teams in the correct methods of pruning. Basic techniques can be taught, but in the UK it takes three years to train an arborist, so we have to be realistic in what we can achieve. I think it won’t be long before I have UK based arborists over there caring for trees. With the 2020 World Expo now secured, the demand for trees can only grow, whilst in Abu Dhabi a new law requires 25% of all ground space on a development to be landscaped – the demand for beautiful trees has never been greater, nor the need of skilled care more evident.