Redesigning a Legacy: 172 New Trees Planted at Seattle’s Climate Pledge Arena

Redesigning a Legacy: 172 New Trees Planted at Seattle’s Climate Pledge Arena

Looking to Grow Your Green Legacy?

Key Facts

334 1st Ave N, Seattle,
WA 98109, United States


Climate Pledge Arena

Swift Company
Oak View Group

Climate Pledge Arena Case Study

climate pledge arena


Located within the Seattle Center, Climate Pledge Arena stands as a transformative redevelopment of a historic site originally constructed for the 1962 Seattle World’s Fair which saw over 10 million visitors.

This multifaceted venue proudly hosts the NHL’s Seattle Kraken, the WNBA’s Seattle Storm, and showcases the world's foremost live music acts and events seating up to 18,000 people.

Named The Climate Pledge after an initiative by Amazon and Global Optimism made in 2019, dedicated to achieving global net zero carbon status by 2040. The construction started in 2018 and the grand opening of Climate Pledge Arena took place on October 22, 2022.


The Next Layer of Trees

render of climate pledge arena redesign

Artist impression of Climate Pledge Arena

Landscape architects, Swift Company were able to protect 107 historic and mature trees around the perimeter of Climate Pledge Arena.

With the planting of an additional 172 trees and 38,000 square feet of new trees and plant areas. Swift Company took a successional forest approach where they looked at the already established mature tree canopy on the perimeter of the arena and designed the next generation and layer of tree canopy.

As highlighted by Swift Company Principal, Gareth Loveridge:

“The entire perimeter was about how do we get more green space and tree environments that invite people in. The more trees we get in there, the more benefit we provide for their daily lives.”  

Using Stratavault for Soil Volume

climate pledge 004 stratavault Citygreen

In most urban settings trees struggle to grow to maturity due to lack of space for tree roots and soil volume.

For Climate Pledge Arena, Stratavault soil cells was key to the planting of new urban trees and increasing soil quantity and volume to already established mature trees around the perimeter.

The demand for robust infrastructure necessitates heavily compacted ground, crucial for supporting above-ground structures. However, this compaction restricts access to vital elements—nutrients, water, and oxygen—essential for optimal tree root growth.

As a consequence, tree roots must work harder expanding their tree roots to find suitable nutrients, water, and oxygen to grow which leads to a reduced growth rate and in some cases tree death due to root girdling.

The 100% recycled plastic stratavault matrix works by taking infrastructure load off the tree roots and soil. Giving the tree and soil a more natural uncompacted growing profile when compared to traditional structural soil planting methods.


broken planting bed details stratavault Citygreen

Infographic on how stratavault grows and protects street trees

The Stratavault system increases the total soil volume available to the tree by over 90%, a substantial improvement compared to traditional structural soil methods, which typically allocate only 20% of usable area to soil the tree can use.

Structural Soil vs Soil Cell stratavault Citygreen

Void Space highlights volume available for tree roots

The increase in soil volume helps improve the performance of the tree ensuring that the tree canopy and the range of benefits across environmental, economic, and healthcare are fast-tracked while protecting the infrastructure and tree roots from damaging each other.

Using Stratavault for Climate Pledge Arena also ensured that the landscape architects could plant larger, more established trees thereby further speeding up the results.

Using Stratavault for Stormwater Management

Strataflow Render stratavault Citygreen

Stratavault also allowed Swift Company to innovate their stormwater management design to incorporate green-blue infrastructure with on-site rainfall and stormwater directed into nearby tree pits through strip drains, pervious pavements, and micro grading of the pavement to direct stormwater.

“It lets the ground plane do exactly what we want it to do, and we’re not making compromises”
Gareth Loveridge, Swift Company

example of WSUD elements being used to feed a stratavault tree pit

Strip drain and snorkil to allow water and oxygen exchange

This allows the trees to detain significant waterflows in the stratavault matrix reducing the strain on the city's municipalities during high rain events while improving the growth rate of the trees as the soil and tree roots use the water for increased tree health and canopy development.

“The water cycle in Seattle is dynamic and there’s plenty of times where we want to slow the water down and soil cells really let us do that” 
Gareth Loveridge, Swift Company

Additionally, using soil and tree roots clean the water of pollutants which ensures that water that does trickle through the tree pit back into the city municipalities will be cleaner.


First Stadium to Earn Net Zero Carbon Certification

climate pledge arena green exterior


In October 2023, Climate Pledge Arena lives up to its name and became the first stadium to earn ILFI certification. The energy profile of a stadium is quite complex, from restaurants, sporting spaces, lounges, offices, retail, and public transport. So, the team had to investigate ways to reduce and sequester their carbon footprint across electricity usage waste, and environmental impact.

During the global pandemic, they redesigned the entire facility to be 100% electric & worked with local energy companies to purchase renewable energy credits as Seattle's reliance on hydropower isn’t recognized by ILFI’s standards and will switch to a newly completed solar and wind farm soon.

Across waste they are working with suppliers to stop the use of single use plastics and they estimate that over 95% of waste is saved from landfill.

Tree Canopy, Living walls, and planting initiatives were major considerations for the landscape with over 12,000 plants and trees planted. The added greenery will help sequester carbon and reduce urban heat through shade mitigation and evapotranspiration of the trees and plants' leaves, and help foster biodiversity in the region.


“We have to address issues of heat island effect and temperature, the integration of soil cells into the fabric of the city is essential to being able to build the tree canopy of a city”

Barbara Swift, Swift Company


Climate Pledge Arena is an environmental legacy that serves over 200 events annually and is at the forefront of carbon performance in the stadium and arena space. The valuable addition of 172 trees will continue to grow, shade, and serve the community for decades to come.

People Enjoying Climate Pledge Arena park

Interested in growing your own green legacy? Book a Free Consult with one of our Urban Greening Consultants to find out how.



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Glenora School Case Study

School Lined with Trees to Provide Shade and Stormwater Detention

Key Facts

13520 102 Ave NW,
Edmonton, Canada


Glenora School

Citygreen PROJECTS

EDA Planning + Urban Design
Cutting Edge Landscapes

Glenora School Case Study

Glenora Elementary School has provided education to downtown Edmonton for the past 100 years. In 2021, it was decided that the school needed a renewal of the amenities to the parking lot, sidewalks, and a general facelift to the school entryway. EDA Planning + Urban Design’s project team decided to take a more progressive step when designing the renewal and really focus on creating a cohesive stormwater management plan.

EDA’s project team established that Citygreen's ‘Stratavault’ soil vault solution was the best solution for establishing a holistic blue+green infrastructure plan


Why Use Stratavault for Stormwater Detainment?

Stratavault is the leading solution for creating ideal underground conditions for trees to grow in urban areas and was key to ensuring EDA Planning + Urban Design could deliver on its blue + green infrastructure plan. The flexibility offered by the matrix design opens up their team with the opportunity for services to be integrated within the soil vault and ensure on-site resources are used efficiently. In this project stratavault delivered in two main areas: 


  • The stratavault modular matrix design enables void space under highly compact urban areas such as the sidewalk and parking lot, providing high quality uncompacted soil to the tree roots. This ensures that we can control the quality of soil the tree needs while the stratavault matrix made form 100% recycled plastic takes the weight of the surrounding infrastructure away from the tree roots.

  • Stormwater runoff from parking lots and rooftops is captured and detained in the stratavault soil cells, reducing the amount of water entering the city's infrastructure during high level rain events and enabling the water to be used locally by trees and soil.

Stratavault being installed at glenora school in edmonton

Stratavault presented the project with an integrated solution that unites rooftop and parking lot stormwater management with landscape tree design. In contrast to traditional methods that channels stormwater into the city's infrastructure, reducing on-site water resources and placing extra strain on municipal systems during heavy rain events, redirecting on-site stormwater into soil vaults offers an effective means of handling the initial rush of rainfall storage.

This stored water can be utilized by the tree roots and soil and subsequently discharged into the city's systems at a later time, promoting sustainability and efficient water use as the soil and tree roots will clean the stormwater pollutants.


Glenora render stratavault Citygreen 



“The biggest value of working with soil cells, specifically the Stratavault system is their flexibility and layout. It's a fully integrated and connected system that can be cut to any shape that you want” 


Will Packolyk
Principal, Landscape Architect
EDA Planning + Urban Design 


How has the Stormwater been used since project completion? 

Will Packolyk from EDA Planning + Urban Design observed minimal effluents being discharged from the system, which indicates how effective using a Stratavault pit is for capturing high level rain events and using the water to irrigate onsite trees is. This not only reduces the strain on the city's infrastructure by managing the initial surge of stormwater but also mitigates the risk of on-site and infrastructure flooding, all while providing a valuable source of water for the trees.

pipes for stormwater management in a stratavault pit

Related: Sustainable ways to Manage Stormwater

The retention of stormwater has also fostered the development of a robust tree canopy and led to a half-inch increase in tree trunk diameter during the initial two years of growth. Will's emphasised the system's efficiency in lessening the burden on the city's infrastructure, enhancing safety and overall well-being for the school community. By redirecting stormwater into a purposeful and sustainable use, such as the Stratavault tree pit, the system not only safeguards the school but also ensures that vital public spaces remain accessible and safe during severe weather events.

Glenora School Render stratavault Citygreen

Is Blue Green Infrastructure the future of Stormwater Management?

The decision to use stormwater runoff to nourish the trees represents a industry shift in the way stormwater is being managed in urban landscaping developments. This synergy between stormwater management and urban forestry takes a page from nature to create a sustainable ecosystem not usually present in urban environments. Trees, with their deep-rooted capacity to absorb water, not only thrive in the conditions soil vaults create, also actively contribute to the improvement of air quality, the mitigation of the urban heat island effect through shade and evapotranspiration, and increase the overall aesthetic of the space.

The integration of the Stratavault soil vault for stormwater management has proven to be a multi-faceted success story and we believe stormwater management that uses both blue and green infrastructure is the future making it a model for sustainable urban development.


‘Stratavault is by far the easier product in this technology to worth with. It is simpler to train our staff. It allows less opportunities for mistakes, due to the simplicity of the install and the structure."

Kris Sloan
Cutting Edge Landscapes 


What Trees were Planted? 

glenora case study 001 stratavault Citygreen

Japanese Lilacs were chosen as the ideal tree species for this project due to their suitability for the Canadian climate and their numerous benefits for a school location. These trees, with their compact and sturdy nature, offer more than just shade; they have showy, fragrant blooms that will enhance the aesthetics of the school's surroundings. Additionally, their resistance to most pests and diseases makes them a low-maintenance choice, aligning perfectly with the school's commitment to sustainability. 



Citygreen Urban Greening Consultants are available to sit down with you and explore how we can transform your urban space into a thriving, sustainable, and environmentally friendly environment. Whether you’re a municipality or landscape architect our team is available to design, install, and deliver better outcomes for your trees & stormwater management strategies.   


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Stratavault Empowering Tree Planting in Tamworth CBD

Stratavault Empowering Tree Planting in Tamworth CBD

tamworth fitzroy street stratavault grown trees

Key Facts

Fitzroy Street
Tamworth, NSW 2340


Tamworth City Council

Citygreen PROJECTS

A Vision for a Vibrant CBD

Tamworth is a vibrant regional city located on the Peel River in the middle of New South Wales. Known as the ‘Country Music Capital of Australia’, it is celebrated for its rich musical heritage and hosts the internationally renowned Toyota Country Music Festival Tamworth. Beyond its musical fame, Tamworth boasts a diverse and thriving community, offering plenty of country charm.

The heart of Tamworth CBD, Peel Street, is a hub for distant towns and farmers to visit, work and play. During Tamworth's famous week-long ‘Toyota Country Music Festival’ Peel Street is closed to traffic and transforms into a lively pedestrian thoroughfare filled with bustling markets and lively buskers and performer stages up and down the street.

Recognizing the opportunity to breathe new life into adjacent Fitzroy Street, Tamworth Regional Council embarked on a comprehensive revitalization project in December 2017 to help integrate the underutilized street into the CBD and help bring life to the businesses by adding a place for people to congregate with lighting, trees for shade, and street furniture with misting and ‘living umbrellas’.

Tamworth Fitzroy street chinese elm trees in stratavault next to street furniture

Tree Growth Comparison

In 2023, Citygreen conducted a site visit and observed the impressive growth of the Chinese Elms since their planting. Citygreen's Stratavault infrastructure plays a vital role in supporting this remarkable tree growth. By providing an optimal environment with uncompacted soil, the trees can establish extensive root systems within the vault.

growth comparision of tree in tamworth fitzroy street

This innovative design not only prevents root damage to city infrastructure, such as roads and pavements, but also ensures that the trees receive essential water and oxygen. Permeable pavements allow oxygen and rainfall to seep through the pavement into the soil vault enabling the root system to breathe, while a snorkel system with integrated piping is included at the base of each tree.

This system enables Tamworth Regional Council's team to effectively hydrate and manage the trees, even during the frequent droughts experienced in Australia's harsh climate.

fitzoy street comparison from 2015 v 2023

Development of Fitzroy street into a pedestrian focused CBD street.

Benefits to the Community and Businesses

The tree planting initiative in Fitzroy Street has had a profoundly positive impact on the community and local businesses. The once-dull streetscape has been completely transformed into a vibrant and inviting environment adorned with lush greenery. This visual enhancement has greatly improved the aesthetics of the area, creating a more appealing and welcoming atmosphere for residents and visitors alike.

Fitzroy street concept plan

Moreover, the revitalized streetscape has not only enhanced the overall appeal of Fitzroy Street but also positively impacted local businesses. The presence of greenery and the inviting ambiance created by the trees have attracted more foot traffic to the area. 


“Fitzroy Street is now truly part of Tamworth’s busy CBD, and is particularly popular during Tamworth’s hot summers as a great place to take a break while shopping in Peel Street.”

Tamworth Regional Council


As a result, businesses located along Fitzroy Street have experienced increased visibility, footfall, and customer engagement. The combination of natural beauty, shade, and a pleasant atmosphere has made the street a desirable destination for residents and visitors, ultimately contributing to the economic growth and vitality of the local community.

Advantages of Stratavault for the Project

stratavault being installed in fitzroy street tamwoth

Stratavault installed in curved pit


Citygreen Stratavault™ revolutionizes tree-planting projects in urban environments. By maximizing soil volume for tree roots and providing a stable base for roads and pavement, Citygreen Stratavault™ ensures optimal conditions for thriving city trees. With its robust and interconnected module matrix, installation becomes effortless, allowing trees to flourish in even the most challenging environments.

Tamworth Regional Council worked with specialized consultants on the project and their selection of Stratavault for this project was driven by the several key advantages it offered:

Stratavault was selected for this project due to the significant quantities of underground utilities located in Fitzroy Street, which were constrained by significant stormwater infrastructure, water, sewer, power, communications, and gas services. This meant that containing the root systems of any new trees planted was a significant concern, which was alleviated through the installation of Stratavault. As Fitzroy Street was seen as a multi-use development, the two vault sites are also located with the area intended to carry traffic loading during events”

Tamworth Regional Council

stratavault installation in tamworth fitzroy street

Stratavaults innovative design facilitated ideal growing conditions, root containment, and protection of underground services while promoting healthy tree growth. Additionally, its load-bearing capabilities ensured durability, making it ideal for a multi-use area such as Fitzroy Street.

A Commitment to Sustainability

The commitment to sustainability is at the core of the Tamworth Regional Council's vision for the development of Fitzroy Street. Although the initial plan did not include a complete tree canopy cover, the importance of maintaining the shade provided by the existing trees has become a long-term priority for the council.

Tamworth Regional Council recognizes the significance of green spaces and the benefits they bring to the community and the environment. They are dedicated to the greening and cooling of the region, aligning their efforts with their Blueprint 100 strategy. This strategy emphasizes a responsible and sustainable approach to urban development, aiming to enhance the quality of life for residents while preserving and protecting the picturesque landscape Tamworth inhabits


The project stands as a testament to the positive impact of strategic tree planting and sustainable urban development. Through the innovative application of Stratavault, Tamworth's surrounding CBD was able to be better utilized and incorporated into the greater CBD streetscape for a greener, more attractive environment. The project's success is evident in the revitalized streetscape, the community's enjoyment of shaded areas, and the long-term commitment to sustainability.

If you are interested in learning more about Stratavault or would like to talk to one of our Citygreen Consultants about an upcoming project. Contact us below

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Revitalizing Orange CBD

Revitalizing Orange CBD: The Impact of Stratavault Tree Planting

Key Facts

Lords Place
Orange, NSW 2899

November 2022

Orange City Council

Citygreen PROJECTS
Sala4D Landscape Architecture

About the Project

In late 2018 Orange City Council engaged urban designers and architects sala4D to develop a plan for upgrading the CBD.

The last significant upgrade of the Orange CBD was undertaken in the 1990s. Since then, the way people and communities engage with the CBD and retail sectors has changed and evolved. The community asked for more places where they can gather and spend their time in attractive, fun spaces.

tree planting in stratavault soil vault at lords place orange

Project Goals

The concept plan for Lords Place South aims to make the city center more attractive and pedestrian friendly. The proposals include doubling the number of trees, introducing eight raised platforms for outdoor seating and dining, and creating nine new open space areas with trees, shade, and seating. Improved street lighting is planned to boost the nighttime economy.

With these tree plantings the number of car parking spaces in the area would be reduced by a third, from 67 to 44 to accommodate these changes

Artist Rendering of Lords Place, Orange

Artist Rendering of Lords Place, Orange

Project Challenges

Initially, there were 16 trees in Lords Place South; however, due to the new construction, and review of the current trees it was decided that 10 of them need to be removed. Similar to other trees in urban inner-city areas, the existing trees in Lords Place South encounter difficulties as their roots are largely covered by concrete and bitumen. Additionally, being planted in structural soil restricts the growth potential of their roots.

A huge community concern around the tree planting was the transition from a car-focused street to a pedestrian-focused street and the loss of car park space for businesses. Citygreen were able to mitigate the loss of car parking space by double planting of trees diagonally in line with the space of the carparks. These trees share the same treepit, an advantage of sharing the same treepit is that less soil volume is needed per tree overall as there is an overlap in soil use. At completion of the project there is now a total of 28 trees in Lords Place South.

Drone shot of Lords Place Orange, showing stratavault tree planting


The presence of existing underground utilities posed a significant risk to the project. However, with the modular design and large void spaces of the Stratavault system, the matrix can easily be built around utilities with minimal changes to the design; making Stratavault system the ideal solution.

Worker preparing existing underground utilities for stratavault tree planting installation


Why Stratavault?

As part of the FutureCity program, new trees have been planted in Citygreens Stratavault matrix. These soil cells prevent the roots from spreading and causing damage to nearby infrastructure such as roads and underground utilities while providing the tree with optimal soil volume and compaction to ensure ideal growing conditions.

Another advantage of using Stratavault in busy urban areas like Lords Place is that the 100% recycled plastic modules are weight-bearing and designed to be trafficable, meaning cars can park safely alongside the trees without harming their roots. This approach helps minimize the loss of parking spaces, as the trees can be strategically positioned to maximize parking availability along the street. Additionally, the Stratavault Matrixes are connected to the city’s stormwater channels, allowing the trees to thrive by intercepting water runoff that would normally enter the city’s infrastructure and be taken out of the area.

There are a few main benefits when considering this approach:

  • Sustainable water utilization: The connected system allows for the harvesting and utilization of rainwater for irrigation purposes. This reduces reliance on municipal water sources and promotes water conservation.
  • Phytoremediation: Tree roots and soil microorganisms help remove pollutants, sediment, and nutrients from the water, improving its quality.
  • Enhanced urban cooling: As the trees in the Stratavault system receive ample water, they can provide better shade and cooling effects in urban environments. This helps mitigate the urban heat island effect and creates more comfortable outdoor spaces for residents and pedestrians.
  • Stormwater Management: Storage of water in high rain events helps to reduce demand on city infrastructure.

Stratavault Tree planting stratavault Citygreen


“It’s a great experience for our city as a whole to understand where the future of tree planting in heavily civil constructed areas can be going with cells in the ground.”

Nigel Hobden,
Manager City Presentation
Orange City Council

Project Outcome

Orange City Council is taking a comprehensive approach to their green-blue urban initiatives, recognizing the valuable role of trees in enhancing the space through aesthetics, mitigating the urban heat island effect with shade and leaf transpiration, and optimizing stormwater management processes by integrating natural processes.

The success of Stratavault soil cells for trees in other locations in Orange, like Kite Street and McNamara Street, demonstrates Orange’s commitment to improving the CBD’s green urban spaces. This ongoing effort aims to attract more residents and workers to the city center while reducing reliance on cars for transportation.

We’re excited to keep an eye on how these trees grow and how the trees will help the CBD evolve the community experience.

Workers Stratavault Tree Planting
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105th Street Edmonton, Canada Green Street Project

The City of Edmonton Strengthens its Core with Green Street Project

Key Facts

Project Location:
105th Street, Edmonton, AB, Canada
Renamed to: Columbia Avenue


Project Partners:
City of Edmonton,
ISL Engineering,
SevenM Construction

Video Case Study Interviewee:
Kyle Wilson & Jeff  Schurek
ISL Engineering,
Cody Mitchell & Chris Payne
SevenM Construction

In September 2016, the second-largest city in Alberta, Canada, celebrated the completion of progressive stormwater management at 105th Street (renamed to Columbia Ave) Edmonton, as part of the Green Street project with the city.



We interviewed the project partners SevenM Construction and ISL Engineering six years after completion to find out about the long-term results and sustainability of the project.
Edmonton’s city limits hold seven sectors, with the mature downtown sector at its core. Surrounding it are six suburban neighbourhoods. Most buildings and infrastructure were built before the 1970s, and the new generation is taking steps to revitalize their city infrastructure and take an active role in stormwater management.

Project Goals

“The city’s primary goals were to revitalize what was formerly a pretty industrial part of downtown,..” said Kyle Wilson, LAT, at ISL Engineering.

“The City of Edmonton identified that the downtown core needed some renovation. It was focused primarily on becoming a walkable corridor that also included bike lanes and focused on non-vehicular transportation,” said Jeff Schurek, Practice Landscape Architect at ISL Engineering.

Upgrades are meant to allow for a flourishing urban forest, in conjunction with a responsibly planned stormwater management system that proves successful “by directing street stormwater into large soil-filled tree pits and draining it through collection pipes at the base of the tree growing areas,” noted Jeff. The ultimate solution for Edmonton’s design challenges was Citygreen’s innovative Stratavault soil cell system.


Project Challenges

The open matrix design boasts unique advantages that present solutions to challenges and considerations like project cost, transport, installation, and the need for green infrastructure and stormwater quality objectives. The cell’s components can nest inside one another and are constructed of lightweight polymers, allowing for significantly lower costs in freight. Once the product is at the installation site, its simple construction doesn’t require unique tools or specialized labour, thus also allowing for a smaller task force.

The Stratavault’s open design allows for the unhindered installation of all necessary subterranean construction, such as water pipes. Even so, with its “quick and simple to assemble” matrix design, the cell system continues to provide the surrounding sidewalks “with sufficient structural integrity to withstand traffic loads,” Cody Mitchel, Project Manager at SevenM Construction, noted.

Project Methodology

The open voids allow tree roots to establish and grow as naturally as possible in the oxygen-rich soil, a thing of the future compared to conventional single-slab planters. These conventional builds have soil too compacted for natural root growth or for rainfall to be properly absorbed and redirected, resulting in unhealthy or dying trees, eroding landscaping, and, ultimately, unnecessary expense in the city’s green infrastructure plans and initiatives.

With 105th Street’s central location inside the city, the active efforts to reduce the damaging effects of unmanaged stormwater levels require large pipe sweeps to be safely integrated into the Stratavault installations. In short, Citygreen’s cell systems offer the city of Edmonton solutions to all the project’s concerns and goals with a single product.

An innovative process “approved by the Stratavault manufacturer” was proposed featuring 200mm, eight-inch water pipes, which could be safely integrated and routed through the cells “with minimal interruption to the structure.” Because the Stratavaults are interlocking and void of bolts or other connectors, individual single-leg sections of the matrix system can be removed for the pipe sweeps, leaving the top layer in place. The sidewalk structure is then reinforced with a bridging section layered on these areas. This engineering modification would not have been as likely with another green technology.

Project Outcomes

Since the project’s onset in May 2015, the first tree pits have been installed and were backfilled with soil quickly and efficiently by Carmack’s subcontractor, 7M Landscaping.

In a final statement on the partnership with Edmonton’s city staff, Biggs reported that the installations are already showing positive results. “This retains the key feature of the Stratavault cell structure – its strength as a connected matrix….” just like the interconnecting streets and communities within the City of Edmonton itself.

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Why Modern Day Living needs more Biophilic Design

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.

living green wall example of Biophilic Designs

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.

Watch our Webinar on green living walls here.

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.

Related: How To Create Sustainable Spaces with Green Living Walls

Screenshot 565 stratavault Citygreen

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 sustainable 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.

How much Soil do Street Trees need?

This question often comes up, in workshops we hold about the urban forest. How much soil do street trees need? Striking the right balance ensures that street trees receive adequate nutrients, space for root growth, and proper water drainage. So what aspects about soil and the underground workings of trees do we have to consider?

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.

example of how tree roots grow

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.

Try our Treepit Costing Tool to find the level of soil a tree needs to support itself once it reach maturity level.

illustration show the imagine vs real way tree roots grow

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.

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Why is the Treepit area 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.

What are ‘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.

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At Citygreen we use Snorkil™ RootRain Urban to ensure oxygen and water can easily penetrate deeper into the soil zone which encourages the tree roots to grow deeper.

snorkil rootrain installed around a tree

How to Calculate the Volume Required for Street Trees?

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.

Another tool we use regularly is the Soil Volume Simulator designed by Elke Haege-Thorvaldson. The soil volume simulator is a great tool designed to give you a rough estimate of minimum recommended soil volume taking in consideration around tree design and height, climate growing conditions, soil suitability, maintenance programs, and expected lifespan of the tree.

You can also review Elke’s recent talk at our event ‘Where the Shade Hits the Pavement‘ where she discusses soil design for landscapes and the soil volume needed.

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.

installation of stratavault to ensure an urban tree has the correct amount of soil to thrive

Comparitive Trial at Ashfield Civic Centre in Sydney

Tree in Stratacell yields 3x larger shade canopy than in conventional structural soil

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About the trial

In February 2011, two different tree pits were planted at the same time with the same tree species (Chinese Elm) at the Ashfield Civic Centre in Sydney, Australia. The tree in the centre forecourt was planted using the Stratacell™ suspended pavement system while the two trees near the sidewalk were planted in structural soil (rock/soil matrix).

Over a year later, the canopy density of the tree planted using the Stratacell system (suspended pavement –  right) is significantly thicker than the one on structural soil (rock/soil – shown on left).


Key Facts

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Ashfield Civic Centre in Sydney, Australia

Structural Soil (Feb 2011)

Chinese Elm (Ulmus parvifolia)





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Ashfield Civic Centre in Sydney, Australia

Soilvault System  (Feb 2011)

Chinese Elm (Ulmus parvifolia)





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These early results from the Ashfield project are well supported by a fascinating study conducted by E. Thomas Smiley, Lisa Calfee, Bruce Fraedrich and Emma Smiley, comparing structural and non-compacted soils for trees surrounded by pavement.

In the 2006 study, Snowgoose cherry and Bosque lacebark elm were planted into five different soil treatment options under pavement, including compacted soil, gravel/soil mixture, Stalite, Stalite/soil mixture, and non-compacted soil.

After 14 months, the study found that there was more trunk diameter growth with the non-compacted treatment than the other treatments. There was also more twig growth, higher relative chlorophyll rating and more root growth compared to all the other systems.

Download the study report as PDF here.

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The comparison showed that the foliar rating with the suspended pavement system was significantly better. Aside from this, “the mean SPAD reading of foliar colour was also significantly higher” as well as “the root length at the rhizotrons”.

The study’s conclusions state that “suspended pavement over non-compacted soils provided the greatest amount of tree growth and health and should be considered when designing urban planting sites for trees”.

Citygreen Stratacell system is an engineered load-bearing matrix that supports pavement and traffic load while providing in excess of 90% uncompacted soil by volume.

Suspended pavement systems, especially those incorporating soil cell technology, are fast becoming the preferred choice for successful urban tree pit design.


We are committed to providing forward-thinking and sustainable outcomes in the urban landscape industry. In order to develop well-planned green spaces across the globe and to help you achieve your vision, we’re now offering Discovery Workshops as an interactive online learning experience.

Book Free Discovery Workshop


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“Great customer service, quick response times and a very in depth QA system with constant support.”

- Laura Wiesenekker, Project Engineer, Densford Civil -

“Citygreen is a very professional  business, and I found everything was great in terms of deliveries, product supply and information. It was all forthcoming and helped us to complete the project.”

- Keith Burns, Architect/Designer, Keith Burns Architect -

“Citygreen offered training and invaluable technical assistance during the works.”

- James Callan, Estimating Manager, Complex Co Pty Ltd -

“Our experience, in working with a Citygreen Design Studio was second to none. We found responses from the design studio to be very timely, and technically thorough. We went backwards and forwards a number of times, looking at different iterations of the design and, nothing was too much trouble to examine and explore different possibilities. I would highly recommend the Citygreen Design Studio to any future client considering using your services.”

- Sandra Smith, Principal Landscape Architect, City Of Monash -

“We are big on compliance on all projects, and the fact that their SmartCertify cloud platform covers all bases, and supports their 20 year warranties, is critical – especially that these pits are being installed under roadways and footpaths.”

- Johny Purkaystha, Civil Program Engineer, Central Coast Council -

"I reviewed all the previous projects that we have installed in the past couple years using your product and I can happily report back that we have 0% mortality in the soil cells, which is incredible!"

- Brendan Wilton, CEO, Trim Landscaping, Bedford, Canada -