This is the third in a four-part series. In previous articles (links at bottom) I talked about the spontaneous regeneration on brownfield sites in the UAE and the utilisation of seeded landscapes to create semi-natural ecosystems without irrigation. Another factor of these landscapes would be to make them productive in a way that would enrich the soils of not just that landscape but, by the production of useful products, returning fertility to the soil for both the site concerned and also urban landscapes and gardens elsewhere.
Coppice woodland is not a term that you normally associate with the Middle East, yet there are many trees, both native and introduced, that would work in this manner. So what would be the point? Well, we have become used to landscapes being either for agriculture, or for ornament, yet this simplification overlooks the fact that we can have landscapes that are multi-functional and that they can also be productive in other ways.
To understand this concept, we should look to agroforestry, or forest gardens, where multi-functionalism is the order of the day. We think of these systems as being in tropical or temperate regions, yet there are many plants that can be organised and used in this fashion in arid lands. I want to focus this article on one aspect only, the production of biomass. Biomass has multiple functions: the production of poles for building and firewood, compost, and when shredded, mulch. We can produce biochar, which is seen as an increasingly important part of long-term soil enrichment and carbon sequestration. There are also food and fodder crops which would be a valuable product, dependent upon species. And of course, verdant biomass supports verdant wildlife.
Many of these plants are also nitrogen-fixers and these are especially valuable for building fertility and assisting the development of other species. Whilst some may have allelopathic properties, which inhibit the germination of other seedlings within the root zone, my general observation is that this is not particularly effective, nor a problem.
So a list of trees that would grow in the Middle East unirrigated, can be coppiced and are nitrogen fixers, would include:
Acacia (Senegalia) senegal
Prosopis cineraria (possibly)
Other species, coppicable but non-nitrogen fixing, would include:
Azadirachta indica (assumed from observed regrowth)
Conocarpus lancifolius (assumed from observed regrowth)
There will be many other species that could fit these lists, but it’s a start. Many ornamental trees, such as Millingtonia and even Delonix show tendencies to throw up epicormic growth from wounds and therefore, in theory might coppice, but I am concentrating on trees which can do this without irrigation.
It’s important to say right here that this shouldn’t ever be designed as a monoculture; there is sound ecological reasons to to maximise the diversity of a planting. Naturally, you wouldn’t use everything, for conditions will suit some better than others for any given site. Nor would you coppice everything all at the same time. Staggering the harvest evens out the work-flow but more importantly, creates communities of plants at different stages of growth. The “edge zones” are always where the greatest biodiversity occurs, for you get the overlap of differing ecologies. Whilst each species will have it’s own regrowth rate and optimum cutting cycle, this can also be varied, according to the use of the product.
Of course, there is a problem, for many of these species are incredibly thorny, which is a real issue for those carrying out the coppice-work. Young vigorous growth also tends to have the most vicious thorns! On a larger scale, it may be possible to use forestry-style Forwarder tractor-trailer units to collect the brush and load it directly into the chipping machine hopper, without human intervention. Someone’s still got to cut it and do initial handling though.
So how do we express this idea, of coppiced woodlands, arid-land style? it would depend on context but there are several approaches we could take. On a large scale, machine operated (as mentioned above), we would have to do traditional layouts with alleys or rows, firebreaks etc. Mixed planting though, would be preferable although strips of one species are possible. If kept narrow, with different species to either side, the effect ecologically would be similar to mixed planting.
In smaller areas, or where human interaction is intended, then these could take the form of the mixed, seeded landscapes that I discussed in my previous article. In other words, we can combine the function with the elements of aesthetics and ecological diversity. Not to mention desert reclamation. Remember, all this is proposed as unirrigated land. The verges along main roads are a prime candidate, instead of over-manicured lawns and hedges that you see at many junctions.
My next article will discuss design, the knowledge and training needed for the creation of such landscapes. I believe we could transform the landscapes of the Middle East, without the intensive irrigation that is required by conventional approach.
In part one of this four-part series, I discussed the colonization of brownfield sites in the UAE’s cities with a range of trees and shrubs – almost all of them “exotic invasive” species. I argued that these could be forming the basis of new, adapted ecologies. To revise those arguments, please the link at the end of this article. The next question is, once we accept this premise, how do we create these new ecologies as a conscious expression of our own adaptation to climate change?
First, let’s understand that we need these landscapes to be unirrigated. Why? Well, in the Middle East especially, water is a precious resource and expensive; the UAE is particularly bad, with a per capita use of 550 litres/day. So with landscaping, let’s keep the irrigation for the urban centres, parks and gardens. If we just focused, for example, on all the miles of roads and interchanges between Dubai, Abu Dhabi and Al Ain that are irrigated, and imagine these replaced with unirrigated greenery, the water saving from this alone would be massive. Yet that is an immense challenge, for as soon as you plant something in a desert, you must water it.
If we want a vibrant plant ecology, then we also need a vibrant soil ecology, something that conventional landscaping ignores completely
I think this is the key, that planting in such a climate rarely establishes without help, whereas seeds can. What we need therefore, is a methodology of establishing and maintaining, seeded landscapes.
It is true that in a scenario where we are consciously creating an unirrigated landscape, we would want to greatly increase the odds of establishment. In this respect, much detailed assessment would need to be given to soil amelioration. If we want a vibrant plant ecology, then we also need a vibrant soil ecology; this is crucial and something that conventional landscaping ignores completely.
Can we create a healthy soil, rich with microbial activity and naturally water retentive in such an arid climate? I think we can, but we must first change our thinking from one of assisting landscapes with external inputs (irrigation) to that of creating self-sufficient ones, with cyclical, living, self-sustaining ecologies. Soil becomes the vital kingpin in all this, not just an anchorage medium for plants.
Native soils need to be worked with, not replaced. They can be moderated, made more moisture retaining, but basics like salinity and pH will always dictate plant choice. First and most important, is to increase the soil’s water retention capacity. There are a number of ways to do this, involving additives which may incorporate clays, granules or other water-holding mediums and we know that when used in irrigated landscapes, they can reduce water demand by up to 50%. Given that an unirrigated landscape might have periods of time when it is extremely dry, we need a medium that doesn’t become hydrophobic if it does dry out and that will react swiftly to absorb water when it does arrive.
We can also inoculate the soil with mycorrhizal fungi cultured from local, healthy environments to enhance soil micro-ecology; there is little point in importing this from another part of the world, as the relevant strains of microbes are likely absent. Microbes and bacteria are the essence of good soil. Many of the plants used will be nitrogen-fixers, and so live in a symbiosis with certain bacteria. They also make nitrogen available to other species, as cycles of life and decay build up.
Organic matter is also essential, but perhaps the most problematic element as it is in short supply. One aspect of the practical usage of such landscapes, and a part of the long-term management, can be the coppicing of trees and shrubs for biomass to make compost. Organic matter tends to oxidise if conditions are not conducive, so we need to get things right, but I’m sure that even desert soils can sequester carbon, given the right conditions.
We would need to mix these various elements into the soil to the appropriate depth, perhaps a metre, probably by air injection, and possibly to different depths for the different mediums. Soil preparation becomes the most major, one-time investment in the land but will pay back endlessly over the lifetime of the landscape.
Once the preparation is done we have to seed the land, when conditions are optimal (not when contract deadlines require); this would have to be timed after rain, if possible. Otherwise, I would give the land a soaking, with our soil amendments helping to retain the moisture, then apply seed, in a variety of ways, possibly by hydra-seeding. Finally, a locally-sourced stone mulch should be placed over all, to again help retain moisture, but not too thick to inhibit germination. This would be the entirety of the preparation and installation work.
Next is the nurturing stage, followed by on-going management and maintenance; this will be very different from a conventional landscape, but no less intensive, at least for the first few years. It may be beneficial to give additional watering to aid plants as they germinate and establish, but this must be done with care, or seedlings could be washed away. We would need to give enough to ensure success, but no more.
Once established, these plants would grow at whatever speed the conditions allowed and a new landscape would emerge over time. Thinning out and reseeding of failed areas would be the main work, acts of stewardship rather than maintenance. Prunings shredded and spread as mulch, soils fit to support life, insects, animals and birds would soon make this place their home. The result would be a slow and genuine landscape uplift into the realms of a new and adapted ecology.
How we design such landscapes, choose which plants to use, obtain the seed and know how to maintain them, is the subject of the next article.
This is the first of a four-part article, links to the others are at the end.
These articles are all a part of the same thought progress, which has been brewing for some time and started with an article I wrote two years ago, in March 2018. I think this is an important subject, and hope that you’ll agree and read them…
Whenever I am in the UAE, I find time to visit various parks and gardens; on my latest trip to Dubai (February 2020), I went to see Al Ittihad park, a well-kept secret in the spine of the Palm Jumeirah, underneath the monorail, which was designed using native and naturalized plants of the UAE. It also, the blurb said, promised everything was labeled, so ideal for a crash course in local flora. The park was interesting but unfortunately all the labels had gone, and it was being maintained in the manner of all landscapes; incorrectly, especially so for native planting.
Of equal or greater value, however, are
simple walks around the back-streets and suburbs of a city and I find empty
brownfield sites, awaiting development, often offer the best insights as to
what will actually grow in an arid region, if things are left to their own
devices. It’s more than you’d think, and
it’s not all native. I’ve written about
this before, in this article and I’m building here on my earlier observations.
The world is gripped in fear of biological invasion, currently of Coronovirus but I’m talking here of the floral kind. Globally, there is a growing passion for conservation, restoration of what was, of what we think of as native and right. We seem to think that in taking this approach, we are setting right the wrongs we have done; nothing could be further from the truth. Fortunately, Nature doesn’t share that passion and is busy dispersing its flora and fauna around the place, wherever and however it can. That it uses humans as vectors for that dispersal, is obvious, if you just look upon it from a wider perspective. Perhaps Nature knows something that we humans are trying hard to ignore; that the climate is changing, the rules of life are shifting, that ecologies need to adapt to the new conditions.
I think we humans are both arrogant and ignorant when we say, “that plant doesn’t belong here, we must get rid of it”. Plants that arrive and succeed are the pioneers of a new, adapting ecology; yes, they are aggressive, yes, they grow without restraint and colonize -usually – disturbed ground, yes, some make monocultures. Like all pioneer species they are fast, competitive and relatively short-lived. But they establish life and the conditions for the next species of successional plants to come along. All parts of the world are, or soon will be, under such huge environmental stress that we must actively embrace change and nurture these new ecologies. We cannot live in a world without complex ecology, nor can we hold back the change, so we have to go with it.
To come back to my brownfield sites, on
my previous article, linked above, I encountered the following trees growing on
a brownfield site in Abu Dhabi:
From recent observations in Dubai I can
add the following trees:
Plus the Prosopis and Ficus from the above list.
From the looks of it, this site was
more recently cleared than the Abu Dhabi one, and trees appeared to be no more
than 2-3 years old.
There were also a range of groundcovers
and grasses growing; I haven’t been able to ID them all, but some I saw
Such plants are equally important in
building new ecologies, and a big part of the whole. There are of course, a huge range of native
or adaptive plants not represented here, which would nonetheless grow, given
These observations might be interesting, but how useful are they? If we think of conventional, irrigated landscapes, perhaps not very useful at all; we know and use many of the trees already. Where this becomes interesting, is in that they self-seed and establish without any human intervention. If we could master the art of this, then such landscapes we would nurture and manage, with occasional thinning, removals, perhaps some sucessional seeding or planting. Imagine this on a large scale, in peri-urban locations, alongside roads, at intersections, instead of the over-watered ornamentation we see now throughout the UAE. We then save the ornate for the urban parks, streets and gardens.
Could this be the basis for a new approach to creating landscapes and if so, how would we do it?
Gravel gardens have been around a long time yet with a few well-known exceptions (Denmans, Beth Chatto and more recently, Olivier Filippi), never really make it into the mainstream of garden design. I suspect that for some designers, there is insufficient structure to satisfy, yet that is actually one of the main benefits. This makes them low-impact, from a carbon perspective, and naturally adaptive, with the kind of planting they use.
I have been designing such gardens for the past twenty plus years, and a part of my own garden is gravel, on the area of an old driveway; it’s the part I enjoy the most. Unlike perennial borders, there is structure all year round and I often wander around in the depths of winter, enjoying the shapes and forms, or the scent of rosemary (sorry to say, now officially Salvia). It’s like you’ve brought a little bit of the Mediterranean into the garden. Plants self-seed around and it’s always a bit different every year. It’s a style also eminently suitable for the arid regions of the Middle-East, whether xeriscaped, or not.
Not everywhere is suitable for a gravel garden and the obvious criteria of sun exposure and poor(ish), free-draining soil are a must. Whilst drainage and soil structure can be altered, aspect cannot. The other factor, frost/cold exposure is actually not such a barrier, although it will limit the plant choice a bit.
Some years ago I was tasked with turning an old farmyard on the South coast of England into such a garden. The compacted rubble was on average 50cm deep, so we loosened and/or removed about 400 tons and replaced a similar amount of topsoil into slightly contoured mounds. As it was a farm, the soil was already available stacked on site and there was somewhere to remove the rubble to. We then rotovated 50cm of gravel into the mounded soil to improve drainage and planted with a range of “Mediterranean” plants. Most were from this region, with some Australian/New Zealand species, most notably Phormium (which I probably wouldn’t use today). We also built a stream and water feature, using 30 tons of boulders (glacial, so not strictly true to theme).
If I were doing this today, I’d leave even more of the rubble in place and blind the soil in over it. Over time I have come to realise that such conditions are an advantage, and expected by many Mediterranean plants.
We used a drip irrigation system for the first year of establishment, which was then switched off in the second year. A 50mm deep dressing of 20mm diameter marine shingle covered everything, including the paths, which were left from the original, compacted sub-base.
I tracked this garden for a few years until the property changed hands and learnt some valuable lessons (as you always do), such as don’t put too many larger growing shrubs in, as the openness of the spatial structure becomes compromised. Whilst they are good at establishing initial structure, be prepared to remove some of them as the garden matures. Some, like the Cotinus and Tamarix, were meant to be coppiced every few years, but didn’t have this done. Some perennials work better than others and low mounding shrubs are what make the predominant visual structure of the site.
This last two pictures, plus the header, are a part of my own gravel garden, created over an old driveway, where I constantly experiment with new plants and slowly expand it all.
Gravel gardening has much to offer and is an appropriate approach for our time, being of low carbon footprint and using plants that are adaptive and generally tough. Have a go, or get me to help…!
The other side of work I undertake in the Middle-East region (other than tree consultancy) is planting design, for creating new landscapes always brings me a special joy. When they are in public spaces, I love the chance it gives to interact (albeit remotely) with many people in place, over time and hopefully, enhance their enjoyment of that place. In the public realm, what that place is, is being questioned and challenged in the light of urbanisation and climate change. Ecology and environment are driving design as never before.
I am about to start working on a collaborative project in Saudi Arabia. It will involve the specification of many trees, shrubs and groundcovers and I get to find out just how many locally-sourced big specimens I can find that are of acceptable quality. Much of this will come down to the application of formative pruning in the nursery and I’ll be on the lookout for the best available in the region. I suspect I’ll be sourcing a lot from neigbouring UAE, simply because of familiarity of sources. Quality remains a challenge, though.
My most pressing concern I have is how to improve on irrigation techniques, which are traditionally massed surface drip lines onto marginally improved sand. This is inefficient and wasteful and I shall be looking at the use of moisture retention mediums and sub-surface irrigation. I believe most watering of landscapes in arid climates could be cut by half, just by more efficient application and retention, in the right place. The picture above shows typical wastage in a Dubai suburban landscape.
Whilst urban planting requires urban plants, I will also be looking at the use of more climate-adaptive species, which I think is important in an era of climate crisis; the Middle-East is going to struggle to cope with every degree of temperature increase. The use of more desert-adapted planting is not new, and not applicable everywhere but I believe there is much scope for experimentation and new thinking.
For me, planting design is about building communities, layering types of plants together in harmonious associations that fit. I don’t mind grouping plants together that come from different geographical regions, but they have to come from a similar ecological niche. Such design is so much more than just nice foliage contrasts and I believe the results can be subtle, but profound.
Landscape must, of course, fit our purpose but I believe we tend to pursue this end to the exclusion of everything else. Nature is the basis of landscape, and so too is ecology, ecosystem and planet. We should not divorce our landscapes from this reality; rather, they should always seek to remind us of these connections. So yes, in town centres and urban streets, we have our eco-bling landscapes; vibrant places, exotic, heady, purfumed, exciting. Nature at it’s most unbelievably flamboyant (cue pic: delonix, the flamboyant tree). Elsewhere, we need more grounded landscapes, more real, more connected to place.
I love this tree, it is everything I have described above, pure eco-bling. Yet it is not appropriate everywhere and because it has become a part of the standard landscape palette, I belive it is overused, and used in places where other species would be more appropriate. I think there are many trees and shrubs that could be used in the region that haven’t been tried yet, from East Africa, for example. The climate there may be more equatorial and more varied but it is not so remote or different as that of some exotics imported from sub-tropical climates (the Delonix mentioned above is from Madagascar, again not too dissimilar).
I think planting design in the Middle-East faces a whole new range of
challenges and opportunities. The changing climate will force new
thinking, to match the new development and the new understanding that is
emerging of our intimate relationship with nature. I’m hoping to
contribute towards that new expression and understanding.
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, provides 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 camaldulensis , 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 camaldulensis , 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.
According to Google, the site has been cleared some time in 2019:
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
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.