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Are living green walls challenging to maintain?

A common concern with living green walls is maintenance, which may put people off investing in this high-value asset – but don’t be afraid!

At Citygreen, we can provide continual support from installation to maintenance requirements for our Citygreen™ Living Wall system so consumers know they are getting the best return on their investment.

Below we have answered the most common concerns people have when they think about living green walls.

Do living walls create water damage to my building?

The Citygreen™ Living Wall systems have a waterproof membrane that prevents water from penetrating substructures.

Do living walls use too much water?

Compared to other greenspaces, the water usage for living walls like Citygreen’s™ Living Wall system is low, as it typically requires two litres per square metre per day to irrigate the wall.

Irrigation is the most critical part of a successful living wall system. In our Citygreen™ Living Wall system, we have designed the vertical irrigation lines to be embedded in a moisture retention layer for optimal water efficiency.

An optional recirculated irrigation system can be installed to achieve further water-saving outcomes.

Will a living green wall work in my ‘space’?

Citygreen’s™ Living Wall system is available in nine standard panel sizes; however, it can also be engineered to retrofit walls on unique buildings. The system is also the lightest on the market, weighing only 35kg per square meter, fully planted and saturated. This means that no additional support structures will be required on small-scale projects.

Also, as discussed above, wherever on the wall the system will be mounted does not require additional waterproofing, as a waterproof membrane is included in the design.

Do living walls require too much ongoing work?

The Citygreen™ Living Wall system comes with remote control monitoring. An advanced automated system ensures the consumer can control the system’s moisture, temperature, ph levels and general conductivity on their computer or phone. This remote capability extends to the automated refilling of the water tanks connected to the wall.

Liquid fertilizer concentrates can also be used in the automated irrigation system to feed the plants. This means that the consumer can easily maintain plant health, but they can also control the pace and vigour of new growth.

Are living walls too expensive?

Citygreen can provide a detailed cost estimate, ensuring that the most suitable living wall solution aligns with your budget.

Are living green walls too hard to set up?

At Citygreen, we will perform a site analysis to determine if any technical installation requirements will be required. For example, if we believe that the indoor installation site is too dark, we recommend using artificial lighting, which we can also deliver and install.

Depending on the site’s location: indoors, outdoors, small-scale, or commercial scale, Citygreen will also assist with plant selection to help find the best species that will thrive into the future.

Assistance will also continue past the set-up stage to the maintenance process, as Citygreen can help will pruning and any ongoing concerns and issues that the living wall may have post-construction.

 Call us Today 

As shown above, Citygreen is an expert in every phase of the design and implementation of living green walls– reach out to Citygreen for a Design Workshop today.

Can trees planted in urban environments capture and reuse stormwater?

In built-up urban areas, trees can help restore pre-development water flows and remove pollutants and filter water. Trees act as natural filtration machines, which can hold and clean water through soil and evaporation.

A question often asked regarding urban trees and water capture is, can stormwater runoff from roads be too polluted for the trees to use?

Yes, stormwater can be very polluted, as large amounts of debris and rubbish can suffocate a tree and prevent water from reaching the tree’s root system for absorption.

Gross pollutants, such as plastic rubbish or vehicle parts, can largely be filtered out often by screens, like stormwater grates.

Smaller than gross pollutants are total suspended solids (TSS). TSS refers to solids suspended in water or wastewater that can be trapped by a filter. TSS can include various materials, such as silt, decaying plant and animal matter, industrial wastes, and sewage. High suspended solids concentrations can cause many problems for stream health and aquatic life.

Then there are soluble or water-borne pollutants, which are difficult to filter out economically. These pollutants can cause serve damage to ecosystems.

Storm water systems can be installed, which prevent these pollutants from accumulating in our water streams. Citygreen offers a revolutionary range of stormwater management solutions that prevent water pollution and make it easier –and more affordable–to manage and re-use stormwater.

Case Study: Pelican Waters

Pelican Waters, a residential estate located on the Sunshine Coast of Queensland, Australia, has been trialling Citygreen’s Strataflow™ system with so far great success.

This new development aimed to use the advanced water-sensitive urban design (WSUD) and improve sales of lots near bioretention basin. Research has shown that preserving natural features in residential developments can increase the value and sale price of lots.

Instead of a traditional bioretention basin, Citygreen’s Strataflow™ uses an underground structural soil cell system, which delivers a high standard of stormwater treatment with a completely natural look.

To any passer-by, what you see is a healthy, flourishing tree, surrounded by a grassy verge, but beneath the ground is an advanced WSUD.

The Strataflow™ is a specialised design ‘hybrid’ tree pit, combining the best urban forestry for sustained and healthy tree growth with fully functional stormwater management – including filtration and flow management.

These designs may start with the Strataflow Kerb Inlet. This device sits in the road kerb alignment, retaining the inherent structure of the concrete kerb. The inlet has a grate (acting as a screen), to stop larger-sized pollutants from entering the system, which inhibits healthy tree growth.

The inlet lets water from the road carriageway flow through the front grate of the drain at a capacity of up to 18 litres/ 5 gallons per second. This allows the inlet to minimise pollutants entering waterways and reduce flood risks by controlling the stormwater flow entering our city’s underground drains.

When the water flows through the street, it enters through the inlet and flows underground. From there, the stormwater reaches the advanced structural soil cell system, where the stormwater is stored, filtered and distributed effectively for the benefit of urban trees and for proper stormwater management.

The inlet ensures the water drains down at the correct optimal depth beneath the pavement height. From there, the stormwater reaches the structural soil cell system and the trees’ root system, where the stormwater is stored, filtered and distributed effectively for the benefit of urban trees and for proper stormwater management.

Essentially, Strataflow™ utilises readily available stormwater rather than potable water to irrigate street trees, which improves the vitality of trees and reduces the impact of stormwater on the local environment, all while maintaining a high natural presentation.

Growth comparison of trees planted in Strataflow (left) and trees planted in grass verge (right)

Call us today

Looking for a cost-effective and sustainable stormwater solution? Contact our friendly Citygreen Team now by clicking here.

What is the best urban tree planting system?

When planting trees in urban areas, there are a few specific elements to consider. The first, and most important thing to consider is that healthy trees require an adequate supply of loose, well-aerated, and uncompacted soil to thrive. This enables tree roots to obtain enough nutrients, oxygen and water so that they can reach their full potential in cityscapes.

In urban areas, where soil compaction is necessary to safely support sidewalks and pavements, conflicts arise when it comes to planting and supporting healthy trees. Over the years, many approaches have been used to help create useable, uncompacted soil for urban trees. Gradually two main approaches have emerged: supported pavement systems, and structural growing media.

Structural growing media

Structural growing media are soil mixes designed to be fully compacted to support vehicles, whilst still allowing tree root growth. An example of a structural growing media is the Cornell Mix, which consists of a blend of rock and soil.

In developing and researching this specific mix, Grabosky and Bassuk (1996) found that there was about 30% void space in a mix of 1.9 cm diameter crushed gravel, which could be filled with clay loam soil. Creating a stone matrix and suspending soil within the matrix pores, meant that the larger diameter rocks would lock together and allow for full compaction, while soil would remain loose for root growth.

Supported Pavement

On the other hand, supported pavement systems involve engineering a pavement so that lightly compacted soil can be installed in a space underneath. Implementing a load-bearing bridge, with low-density soil beneath, ensures that the trees rooting space cannot become heavily compacted.

Studies have found that any system that allows for trees to grow in non-compacted, low-density soil media, will have the greatest chance of achieving healthy tree growth (Rahman, 2013, Fite et.al. 2014, Urban and Smiley, 2016).

Comparison of Soil Treatments Under Concrete Pavement

One such study that Citygreen took part in was titled ‘Comparison of Soil Treatments Under Concrete Pavement’, conducted by the Tree Research Laboratory in Charlotte, North Carolina. The research compared tree root growth using supported pavement systems and structural growing media.

In the study, Citygreen’s Stratacell systems were tested. These structural soil vaults are modular units assembled below pavement level, which meet load-bearing requirements and provide a large volume of uncompacted soil for root growth.

The results of the studies showed that the trees growing in these supported pavement treatments with low-density soil media, had significantly greater growth and generally appeared healthier.

Conclusion

While the study did not point to a ‘best product’, it proved that structural load-bearing modules like Citygreen’s Stratacell and Stratavault systems, provide the best results in urban areas, where compaction is a real issue. For urban planners, landscape gardeners, architects and developers, what this means, is that by simply choosing a structural load-bearing soil system, they can achieve the canopy cover they require years sooner than they might with other systems. Essentially, cities, communities and individuals can enjoy the environmental, economic and health benefits of healthy canopies’ growth faster and for longer.

Have one of the Citygreen contact you

For more information about our products, and how we can help you create greener more liveable cities, contact our friendly Citygreen Team now by clicking here.

Download the full report

To read more about how our system performed the best, in terms of maximum root depth, moisture content and foliar colour, you can Click here to download the full ‘Comparisons of Soil Treatments Under Concrete Pavement’ study.

References

Fite, K., E. Kramer, B. Scharenbroch, R. Uhlig, 2014. Beyond the Great Debate: Assessing Post Installation Manufactured Soils Performance. Presentation ASLA Annual Meeting, Denver, CO, USA. Grabosky, J. and N. Bassuk. 1996. Testing of Structural Urban Tree Soil Materials for Use, Under Pavement to Increase Street Tree Rooting Volumes. Journal of Arboriculture 22:255-263. Rahman, M. A. 2013. Effect of pit design and soil composition on the performance of Pyruscalleryana Street Trees in the Establishment Period. Arboriculture & Urban Forestry 39:256-266. Smiley, TE., Urban, J., and Kelby Fite, K. Comparison of Tree Responses to Different Soil Treatments Under Concrete Pavement. Arboriculture & Urban Forestry. Nov2019, Vol. 45 Issue 6, p303-314. 12p. Urban, J. and E.T. Smiley. 2014. Evaluation of Established Trees – Structural Soils and suspended pavement – Presentation at the International Society of Arboriculture Conference Milwaukee, WI, USA.

Creating sustainable spaces with one green wall at a time

Over twenty years ago, landscape architect, Robert Thayer (1989) examined the importance of sustainable infrastructure. Thayer believed that successful, sustainable design projects ‘symbolize[d] resource preservation through visual, spatial and sensory means.’

Within the context of resource preservation, most people think of preserving natural resources in ecological settings, for instance, creating national parks to protect forests or fencing off wetlands for migratory sea birds.

But what about resource preservation in the built environment?

Rooftops, alleyways, medium stripes, boardwalks, etc. are all resources that can be sustainably preserved and looked after, we just need to change our thinking in this space.

Safeguarding trees within urban spaces, and capturing water runoff from streets, are all forms of resource preservation that can and should be performed within urban settings.

However, Thayer thought that resource preservation within the built environment should go beyond pure utilitarian means and encompass, as quoted above ‘visual, spatial and sensory means’.

A perfect example of resource preservation in an urban landscape that encompasses visual, spatial and sensory experiences is living green walls.

Living green walls are able to sustainably preserve and look after infrastructure in a way that invites modern living to be responsive to ecological beauty.

Aesthetically, green walls exhibit bold, living textures that intrigue people, thus raising our level of participation and interaction with the environment and ultimately improving our sense of connectedness to nature.

In terms of resource preservation, green walls not only protect structures from rain and fluctuating temperatures, they can also reduce noise levels in buildings, and act as pollution filters to improve air quality.

Within urban settings, we, the public, should be able to interact with sustainable and ecological designs, as nowadays a lot of people do not have access to open parklands and gardens, hence why living green walls are a great sustainable design that should be installed more widely.

Living green walls create new associations between the ‘built’ and the ‘natural’, essentially displacing the old normative understanding that cities should be set apart from nature unless it is in park form, where trees, shrubs, flowers etc. can conform to order.

Green walls in one way can hardly be mistaken as natural, yet once planted, they, like any living or interconnected thing, assume a life of their own. They may not conform to an initial design outcome and seek their own patterns, creating more sensory experiences for the public to enjoy.

 

Citygreen’s™ Living Wall system

Citygreen’s™ Living Wall system is a leading example of a sustainable and aesthetically pleasing design for modern-day living. Manufactured by the pioneering brand in advanced living wall products, Terapia Urbana in Spain, this living wall system embodies nearly 15 years of research, development and product testing.

For optimal public exposure, the living wall system can be installed for both outdoor and indoor use. The system comes with artificial lighting, automatic watering and fertilisation systems.

Compared to other more traditional green spaces like outdoor gardens and reserves, the water usage for living walls like Citygreen’s™ Living Wall system is comparatively very low, as it typically requires two litres per square metre, per day to irrigate.

A design feature that allows Citygreen’s™ Living Wall system to stand out, is the fact that the system is the lightest on the market, weighing only 35kg per square meter fully planted and saturated. This design feature enables more flexibility as to where the system can be installed without damaging existing infrastructure.

The design is made up of a three-layer system that all links together, allowing plant roots to have the ability to migrate freely and really take off to create diverse leaf patterns and colours to be enjoyed by all.

 

The design is available in nine standard panel sizes; however, it can also be engineered to fit bespoke sizes for unique projects. The system is also designed for quick and efficient installation for large scale commercial projects or smaller residential projects, with minimum disruption.

Conclusion

For the natural world to be appreciated by the public, it must be seen and experienced, which is why the installation of living green walls is so important, as it enables our increasingly urbanised population to experience nature in a way that is most accessible to them.

Citygreen’s™ Living Wall system, enables both sustainable preservation of infrastructure within urban settings, whilst also allowing individuals the ability to immerse themselves in the beauty of the natural world.

 

References

Thayer, R. 1989. The experience of sustainable landscapes. Landscape Journal. 8(2) 101-110.

Can living green walls help alleviate the impacts of climate change?

Earlier this year, the United Nations Intergovernmental Panel on Climate Change (IPCC) released their starkest report on the impacts of climate change, depicting the threats to both civilisations and ecosystems around the world.

The report documented that the effects of climate change have already impacted human health, livelihoods, and key infrastructure, particularly in urban settings. Hot extremes including heatwaves have intensified in cities, where they have also aggravated air pollution events and limited the functionality of urban infrastructure systems and services.

Essential infrastructure, such as transportation, water, sanitation, and energy systems have been compromised by both, extreme and slow-onset climatic events, resulting in economic losses, disruptions of services and impacts on human well-being.

Through an egalitarian lens, the report observed that these impacts are concentrated amongst the economically and socially marginalized urban residents. Climate change is effectively exacerbating existing social, economic, and environmental drivers of risk, especially for vulnerable groups who already lack access to essential services.

The authors of the report, urgently recommend an appropriate, widespread coordinated effort to adapt our urban environments to more extreme climatic conditions.

They believe that by improving existing and new infrastructure projects, our built environment can become more resilient to climate risks in the long term.

One way of achieving urban resilience is by providing greater access to ‘green infrastructure within our cityscapes. Green infrastructure refers to all types of vegetation that provides environmental, economic, and social benefits such as clean air and water, climate regulation and places for recreation.

An example of green infrastructure that can directly limit the effects of climate change within our urban environment is green walls, also termed living walls or vertical gardens. Green walls can form an important part of a wider strategy to increase the sustainability of our built environments by regulating temperatures and improving air quality.

Regulating temperatures

According to Dr Irga, from the University of Technology in Sydney, Australia

‘thermoregulation is one of the most researched benefits of green walls.’

He explained that ‘green walls can reduce high temperatures within buildings by intercepting solar radiation and through evaporative cooling.’

Conversely, temperature regulation is not just limited to heat reduction, as the insulation ability of green walls can also be of benefit in cold climates too. Through controlling temperatures, green walls enable buildings to be less reliant upon heaters and air conditioners, resulting in reductions in energy consumption.

Improving air quality

The natural, biological processes of green walls can improve air quality in the home and in urban settings by removing polluting air particulars.

The plants used within the green walls can capture airborne particles on their foliage and, with the associated microbial community, degrade a range of gaseous pollutants, including volatile organic compounds (VOCs).

VOCs are generated by motor vehicles, fires, industrial processes, and consumer products like paint. Some are highly toxic and prolonged exposure may increase the risk of health problems.

Aside from absorbing VOCs, green walls are also able to absorb carbon dioxide (CO2). All plants including those grown inside, or on the side of buildings, act as natural carbon dioxide filters. They absorb CO2 from the air to fuel the photosynthesis which allows them to grow and thrive. Presently, more research is needed to determine the most effective CO2 absorbing plants for vertical gardens.

Citygreen’s™ Living Wall system

Citygreen’s™ Living Wall system is a leading green wall product that can directly alleviate some of the risks created associated with climate change, by creating greener, cooler, and more liveable cities.

Citygreen’s™ Living Wall system embodies nearly

15 years of research, development, and product testing.

The design is available in nine standard panel sizes; however, it can also be engineered to retrofit walls on unique buildings.

The system is designed for quick and efficient installation for large scale commercial projects or smaller residential projects, with minimum disruption. The Living Wall system has irrigation lines embedded in a moisture retention layer to ensure optimal water distribution and water efficiency.

This enables both rapid and healthy plant growth post-install.

The assembly of the Citygreen’s™ Living Wall system incorporates a waterproofing layer, a moisture retention layer, and a breathable fabric layer with pockets for the soil so that a wide variety of plants can be selected and grown within the system.

Conclusion

The ability to adapt our urban centres to the unfolding risks of climate change is becoming ever more urgent.

Urban populations, particularly those in marginalised areas, are exceedingly feeling the impacts of more intense weather patterns.

Citygreen’s™ Living Wall system is a product that once installed, can rapidly start to alleviate some of the impacts of climate change, by regulating ambient temperatures, improving air quality conditions, and absorbing CO2.

References
P.J. Irga, et al, The distribution of green walls and green roofs throughout Australia: Do policy instruments influence the frequency of projects? Urban Forestry & Urban Greening, 24, 2017, 164-174.

Why modern day living needs more biophilic designs

As leaders in urban landscape solutions, the concept of biophilic design has been pioneered by Citygreen for almost two decades. Our mantra of transforming grey spaces into green, by incorporating nature into cityscapes, goes to the heart of what biophilic design is all about.

The term biophilia was first used by the pioneering naturalist and biologist Edward Wilson in 1984 when he hypothesised that humans have an “innate tendency to focus on life and lifelike processes.”

This tendency that Wilson speaks to, refers to the bond and deep sense of familiarity that humans and nature share. As a biologist, Wilson viewed life through an ecological lens, comparing lifelike processes to “organisms in an ecosystem.”

He believed that for societies to be functional, their surroundings must be akin to the natural environment that we were evolved in. In the man-made built environments, where most of the world’s population lives today, this sense of connection between nature and everyday human experiences has been slowly eroding.

During the COVID-19 global pandemic, lockdowns forced many of us to live in our neighbourhoods and home on a more permanent basis, which for a lot of people highlighted the lack of, and thus need for more innovative greenspaces.

Generally, the term greenspace invokes images of outdoor parks benches and beautifully manicured gardens, which is too simplistic in terms of 21st-century living. The standard approach in the past for town planners was to allocate a certain amount of open outdoor public space for conventional use, such as walking the dog or picnicking.

Yet today, with modern living requirements and conditions, the inter-relationship between greenspaces and greenspaces users has changed. As individuals, we are now spending more time inside buildings of all kinds, than we ever have before. Therefore, when we think of green spaces we should be contemplating indoor communal spaces like foyers in apartment buildings, food courts, and large shopping centres.

An example of a biophilic design that meets the needs of modern-day greenspace users is green walls, also termed living walls or vertical gardens. Such walls are becoming more popular, as they are able to convert underutilised areas into aesthetically appealing green spaces, by merging the natural and the built environments together.

Using straight walls and rights angles to recreate the scenic irregularities of the natural environment, has been a design goal for many sustainable companies including Citygreen. Green walls that incorporate a wide range of diverse plant species are able to artificially reinvent ecosystems, and can then bring the natural world closer to individuals, whether that be in a bustling inner-city workplace or residential apartment block.

Citygreen’s™ Living Wall system

Citygreen’s™ Living Wall system is a leading example of a modern biophilic design. Manufactured by the pioneering brand in advanced living wall products, Terapia Urbana in Spain, the Living Wall embodies nearly 15 years of research, development and product testing.

The system can be used outdoors, but indoor walls are by far the easiest, as the microclimate is more predictable, with the installation of artificial lighting, and automatic watering and fertilisation systems. Compared to other green spaces, the water usage for living walls like Citygreen’s™ Living Wall system is low, as it typically requires two litres per square metre per day to irrigate the wall.

The three features that make the system unique, and why it is able to stand out amongst other living wall designs, is firstly the fact that the wall, where the system will be mounted, will need no additional waterproofing. Secondly, the system is the lightest system on the market, weighing only 35kg per square meter fully planted and saturated.

Thirdly, the design is made up of a three-layer panel system that all links together, allowing the roots of the plants to be both protected, and have the ability to migrate freely, enabling almost unlimited root volume for the plants to grow in.

The design is available in nine standard panel sizes; however, it can also be engineered to fit bespoke sizes for unique projects. The system is also designed for quick and efficient installation for large scale commercial projects or smaller residential projects, with minimum disruption.

With urbanisation and residential density increasing in our modern-day societies, it is imperative that more cities and buildings be designed and planned in a sustainable way that allows individuals and communities to have equitable exposure to the natural environment.

Citygreen’s™ Living Wall system showcases a leading example of a creative and flexible design that can be used within challenging and ever-evolving modern-day greenspaces.

Learn more – Book Your Free Online Workshop

References: Edward O. Wilson. Biophilia. Harvard University Press. Cambridge, MA, and London, 1984.

Why don’t trees grow well in cities?

In every city, around the world, you see trees that are not meeting their full potential within the urban environment. To the human eye, these trees can appear twisted or have damaged branches, making them unhealthy and deformed.

In serve cases, the trees will gradually decline and end up being removed, with just an open space in the pavement remaining.

Sadly, cutting down dying trees from city landscapes has become all too familiar, and is something we want to explore in this article.

Designing a Tree Planting Method

One of the first reasons for unsuccessful tree growth, in many cases, lies in the failure to fully design a tree planting method. The implementation of any successful method, must first ask questions surrounding the location of the site: what is the soil profile that the tree is being planted into; will there be enough air-filled porosity or oxygen at the depth of planting; does the location have the necessary space to provide for the tree’s root system?

These questions must then be answered by adopting appropriate solutions, such as: applying nutrients to amend the soil profile where necessary; choosing the best-sized tree to fit the location, avoiding having to repair tree root damage to pavements; utilising road-based material that is conducive to tree growth; installing adequate draining mechanisms, so that the tree does not become waterlogged in wet seasons.

Typically, the cities with a healthy and thriving urban forest today, have adopted a comprehensively designed tree planting method to overcome the problem of frequent tree deaths within city landscapes. However, if a tree planting method, like the one discussed above, cannot be fully funded, then tree growing failures in cities will continue to occur.

Tree Planting Budget

To allow trees to reach full maturity, and ideally become self-sufficient, a suitable budget must be allocated. Without a sufficient budget, cities will experience the premature deaths of trees, which will need replacement within 3-5 years of planting.

A well-funded tree planting program would avoid the cost of continual tree removal and replacements, and alternatively appreciate the future value of trees as an asset within any urban environment.

Human Behaviors

Another reason for trees not growing well in cities is human behavior.

This can be broken up into a number of areas, but one is vandalism. Unfortunately, it is not uncommon, to see trees vandalized, especially young trees. Once trees are beyond a certain stage of life, they tend to be less susceptible to vandalism, but while they’re young, they are very vulnerable to being damaged by vandals: debarking trunks; snapping branches; or scratching graffiti onto limbs

Traffic impact is another human behavior that negatively affects tree growth. This frequently occurs with curb plantings, whereby trees are planted close to the roadside. If crown lifting is not performed, and the trees develop a low canopy, then low-lying branches can be smashed and damaged by passing traffic. This is especially the case, where you see a camber on the road that causes tall vehicles to intersect with the tree’s canopy, causing limbs and branches to tear off, allowing infection to set in.

Low-speed vehicular impact in parking lots can similarly impact tree growth. This frequently happens in parking lots, where trees have been planted with the best intentions, but wheel stops have been either omitted or placed in the wrong positions.

For example, at home improvement centers, frequented by trade vehicles with overhanging tray bodies; reverse parking can lead to vehicles, unintentionally smashing into the young trees.  This can be overcome by studying the trees surrounding, to allow for better tree placement and tree protection.

An Altered Environment

The urban climate in which trees are planted can also lead to poor growth performance. Cities have their own microclimate, which is a very different environment to the natural forest. It is well documented that some tree species will actually grow a lot faster in a city than they will in their natural open forest environment, because of the urban heat island effect, leading to warmer temperatures and thus more growth.

However, in a lot of cases, the urban environment does not necessarily result in successful tree growth.  For example, wind velocities in city landscapes are very different to the natural forest environment.

In the forest, trees are protected by one another against environmental forces of nature, but in urban planting, trees are typically planted on their own, and therefore become more exposed.

Adding to this exposure is the fact that the trees are often planted in close proximity to tall buildings, where the street forms a canyon. Winds can then blast up this ‘canyon’ with extremely high velocity, blowing the trees around, causing damage to the root systems.

Oftentimes, the wind will cause a young tree’s root system to be weakened, which may only be noticeable when the tree becomes much larger, unfortunately resulting in limbs breakages, or a whole tree collapses, which can be catastrophic.

Solutions

Fortunately, there are solutions to all of these issues. Citygreen has decades of experience in successfully establishing urban forests to prevent premature tree death. A system that Citygreen has patented and used throughout the world with success is the Stratavault™ system.

 

Case Studies – Stratavault™ system

Downtown Ennis, located south of Dallas, in the United States, is known for its 19th-century historic architecture and iconic brick streets. With its current population of over 20,000, the city was looking to cultivate residential growth.

With this goal in mind, Citygreen’s Stratavault™ system was chosen the make the area more attractive, accessible and beneficial to downtown residents and tourists alike.

Adopting a ‘Green Streets’ approach, the areas impermeable curb and gutter section was replaced with a suspended paving system – that is, Citygreen’s Stratavault™ system, to allow trees to grow and thrive into maturity.

Capable of supporting heavy duty vehicular loading, permeable pavers were installed on top of soil cells which provided a medium for trees to grow in, whilst also capturing stormwater on-site to irrigate the trees.

Citygreen’s Stratavault™ was also utilised to enhance the redevelopment of Barangaroo South, in Sydney, Australia.

Designed to encourage both passive and active outdoor activities, the redevelopment of Barangaroo South’s landscape, initially faced significant difficulties. The density of paved areas and streets, was not able to provide a conducive environment for trees to thrive in.

To overcome this problem, Citygreen’s Stratavault™ was utilised. With its open matrix design, the system ensures that there is enough uncompacted soil space to facilitate strong root growth without damaging the surrounding paved surfaces.

Call us Today

As shown above, Citygreen is an expert in every phase of design, and implementation of streetscape upgrades, incorporating healthy, sustainable green infrastructure – reach out to Citygreen for a Design Workshop today.

How much soil do street trees need?

This question often comes up, in workshops about the urban forest.

Tree Root systems are extensive

The first thing to understand is that the root system of a tree is far more extensive than many people realize. In a natural environment, the root system extends as deep as possible in the soil profile, and typically very, very broadly in the upper layer of the soil profile. Wherever there is sufficient oxygen in the soil, and friability in the soil, to support the root growth of the tree – the roots will explore.

The root plate supports the canopy – but you can’t see it

The root system of the tree provides the structural support for the above-ground canopy, which is the part that we all see. That is a very, very critical function. A tree’s canopy can be very large, is extremely heavy, and is acted upon by the forces of nature – like wind, snow, rainfall etc. Within cities, the power of wind, (sometimes known as wind tunnel effect, or canyon effect), caused by proximity to tall buildings, causes ‘wind-throw’ forces in cities to be much greater than in a forest. So a tree’s root system is critical to anchor the tree physically, and also to support the healthy growth of the above-ground canopy.

A bigger tree requires a bigger soil volume

It’s important that we understand that the amount of soil required is relative to the mature canopy size of the chosen tree species. It’s not related to the size, pot, or box that the tree was grown in at the nursery. The quantity of soil volume that you provide for a tree in the street is all the soil that that tree is going to get – for its entire life. It’s important that the right amount is provided.

What is a tree coffin?

Historically, trees have been planted in small openings in pavements, sometimes called tree coffins. But this has resulted in catastrophic failure in pavements, and surrounding infrastructure, premature mortality for the tree, or consigning a tree to being stunted for its life if it does live. Walk the streets of any city in the world, and you will see this.  So, it’s critical that the concept of soil volume is understood, if we truly wish to grow a healthy urban forest for future generations. The surprising fact is that with the correct volumes of good quality soil – the benefits can be enjoyed within your generation. The growth rates are astounding – we just need to get the basics right.

The Treepit area is really important

Tree roots will grow a long way out from the trunk. Many people have had the experience of having an underground sewer or storm pipe penetrated by a tree’s root system, and the tree was growing a long way away, in a neighbor’s property. Trees will grow a long way out from the trunk – in many cases well beyond the canopy area.

‘Deep Soil Zones’            

The other thing to be understood is the fact that depth of soil is also vital to accommodate the sheer size of the tree root system. For this reason, many cities are now mandating ‘deep soil zones’ for tree planting. This is critical, and is a very good move, to ensure that there is quality soil at a suitable depth, for the life needs of the urban forest As said before, tree root systems will grow as deep as there is adequate moisture, adequate aeration, (oxygen), as well as the essential elements of healthy soil.

So, how to calculate the volume required?

To arrive at a soil volume for a street tree, one simple rule of thumb is to start with the mature canopy size of the tree. Look up reliable tree resources, investigate online, or speak to the tree nursery, and establish what the mature canopy diameter of the tree species is going to be. Generally, this is very readily available. To what width will that tree grow at its full capacity? Then you turn the diameter into the area, by using the area formula. That gives you the area of the mature canopy (shade). Then you take that area, and multiply it by 0.6x a meter, or two feet in depth, to arrive at a target soil volume. Now, this is a rule of thumb, but it’s a very good place to start. There are other, more complicated formulas – but this is a good place to start.

Finding space for deep soil zones

Rarely is there room in a sidewalk, or a parking lot, or a paved area, for the entire deep soil zone to be an open garden bed. Due to pedestrian access demands, and vehicular movements – there is a requirement for extensive use of hard pavements.  The good news is, there are ways of supporting the pavement while maintaining deep soil zones beneath that pavement. But establishing a correct soil volume for street trees is the first step in establishing a healthy and sustainable urban forest, and there are several ways of arriving at target costing based upon this.

To learn more about how to design and implement a successful urban forest project, engage with an expert here.

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