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Structural Soil VS Soil Cells: What’s The Better Choice?

With trees come their roots – and it’s always something that needs to be carefully considered when planting in a city setting.

How can you ensure the roots of your urban trees will grow well under a sidewalk?

What’s the best alternative to make soil conducive for planting, even when it’s located in the city?

For years, people have been relying on structural soil to help trees mature in an urban environment. However, recent developments of soil cell products offer greater opportunities for city trees to grow and thrive in a shorter amount of time.

To help you identify the ideal option for your city, here’s a quick comparison guide about soil cells and structural soil & sand.

What is structural soil ?

People often think that structural soil and soil cells are in the same league. However, they differ in the number of benefits they provide urban tree growth.

Structural soil is a commonly used medium that’s compacted under a pavement system to give structural support, creating only small void spaces for tree roots to grow. It’s made up of 80% gap-graded levels (crushed stones) and 20% soil.

Since structural soil has fewer minerals and nutrients, urban trees planted in it often suffer from weak roots and restricted growth.

What are soil cells?

Soil cells, on the other hand, are purpose-designed urban landscape solutions which equip trees with suitable soil conditions that enable them to flourish without causing damage to local infrastructure.

Soil cells also provide non-compacted soil volumes and an on-site stormwater management system that protects trees from damage.

What are the advantages of soil cells vs structural soil and sand?

Citygreen participated in a study called, “Comparison of Soil Treatments Under Concrete Pavement”.

The research examined the capabilities of structural soil and soil cells in providing root growth space for trees in urban areas.

The study found that soil cells are a superior choice in city environments because of the following advantages:

  • Uncompacted soil within soil cells grow the largest and healthiest urban trees in a shorter timeframe.
  • Soil cells enable the maximum root spread and depth.
  • Soil cells support the weight of tree parts.
  • Soil cells ensure the moisture content of the soil is maintained.

For years, Citygreen has invested in research and innovative development initiatives to explore the challenges, the causes of failure and the reasons for the premature mortality of urban trees.

Through it, we created effective soil vault systems that serve as the most viable solution to help build greener cities.

To learn about our cutting-edge technology, head to


Cleveland’s Approach To Restoring Its Canopy

Cleveland was once a Forest City with 26 different tree types and 94% tree canopy coverage.

However, the promise of industrialisation and modern living have sadly left the city with only 19% of tree canopy by 2019. While the number of tree species has remained intact, the quantity of each variety has decreased substantially.

Different organisations across the city are now making a genuine effort to restore Cleveland’s tree canopy in an attempt to ensure there are enough trees to sustain a better quality of living within their city – today and into the future.

What is Cleveland’s present situation?

The Cuyahoga County Urban Tree Canopy Assessment reported in December 2019 that the coverage of the local tree canopy has diminished from 37% to 35% between 2011 and 2017.

This 2% loss, while it may look small, equates to 6,500 acres of trees or 5,000 football fields. But more than anything, this dwindling tree canopy causes detrimental effects to public health. Trees provide sufficient shade and clean air, which can eliminate stress and reduce respiratory and heart problems. Without them, citizens can often be more susceptible to sicknesses.

Cleveland Tree Coalition found that due to Cleveland’s tree canopy, there are 1,200 fewer incidences of adverse health effects such as hospital visits and respiratory symptom every year!

It’s no surprise, then, that the well-being of the local communities will be negatively impacted if the consistent and considerable loss of their tree canopy continues.


What is Cleveland’s solution?

With the support of public officials and local residents, Cleveland Tree Coalition has been paving the way for the restoration of Cleveland’s tree canopy since 2015.

They have planted over 2,500 trees already, but still need to grow 350,000 more in the next 10 years to improve the city’s tree canopy from a 19% to 30% coverage by 2040.

Since larger species of trees create a wider canopy, part of their strategy is growing the right kind of trees, like Honey locust trees. Cleveland City Council has also implemented a policy in 2018 that requires Developers to add tree preservation plans into their development projects, ensuring that any trees that are removed during construction will be replaced.

Cleveland’s volunteers are aiming to increase their efforts in upkeeping their current trees and maintaining the health of those they have recently planted. That’s because spending millions of dollars planting new trees won’t produce great results and returns in the long run if they die in just a few years.

At Citygreen, we support these kinds of tree planting and maintenance initiatives.

That’s because we believe that having more green spaces is the key to better living, especially in cities. This is why our team of experts and project consultants research best practices and approaches to allow trees to live harmoniously alongside the advancements of every city.

We have tree products and solutions to ensure every city can cultivate healthy green spaces for their local communities.

To learn about our urban landscape solutions, head to

5 Reasons Why Soil Quality Is So Important For Trees

Everybody knows that soil is the foundation for tree growth!

However, not all soils are the same, and that can have a significant impact on the trees growing from it.

Cultivating the right kind of soil will ensure trees will live and thrive, even in urban locations where there is less room for them to survive.

That’s why it’s so important to take note on what’s happening below ground, if you want to enjoy the beauty and shade of the greenery above.

Let’s take a closer look at soil and its importance for healthy tree growth.

What makes up soil?

Soil is composed mainly of elements like water, minerals, nutrients and gases.

Different types of soil vary according to texture, colour, depth, acidity, fertility and ability to hold water. Because each tree species has different needs, it’s crucial to know what kind of soil they require to grow – if you want the best results.

To help familiarise yourself with the varieties of soil, here are the most common types of soils you need to remember:

  • Chalky – a stony type of soil that can be found on top of limestone or bedrock
  • Clay – a tightly packed soil that is often lumpy and sticky when wet
  • Sandy – dry and loose soil base that has a rough texture
  • Silt – smooth, slippery kind of soil that is composed of fine particles
  • Peaty – contains a great amount of organic matter due to its acidic nature
  • Loamy – the best soil for planting, as it’s full of nutrients and can hold water well

Why is soil important for tree health?

The soil you use can either nurture or restrain your trees’ growth because soil performs a lot of essential functions. Here are the five reasons why soil is important for trees:

  1. Soil provides a foundation for tree growth.
  2. Soil stores the necessary amount of water for trees.
  3. Soil hosts biodiversity.
  4. Soil supports the trees’ roots in accessing nutrients and minerals.
  5. Soil filters out the pollutants that can harm trees.

In urban locations where healthy soil is not abundant, it’s important to ensure that trees are planted with the appropriate soil structure to compensate – often called the “architecture of the soil.”

Having the right soil architecture guarantees that there is proper arrangement of soil particles (including silt, sand and clay that aggregate together). It also involves measuring the correct pore spaces between each tree, which enables their roots to propagate without causing any structural pavement damage.

When these two considerations are overlooked, trees will struggle to grow in city and suburban locations, leading to replacement and maintenance costs, unsightly spaces and poor shade quality for the community.

Citygreen understands this challenge.

That’s why we deliver innovative urban landscape solutions like Soil Vault Systems. Our very own Stratavault© and Stratacell© tree products facilitate healthy root growth for your trees while making sure they won’t cause any damage to your city’s infrastructure.

To find out more about these products, head to


How To Properly Water Your Trees

While people are supposed to drink about eight glasses of water a day, a tree in Ohio with a 10’ canopy can require as much as 100 gallons a day!

There are a couple of crucial considerations when it comes to watering trees. Insufficient water can lead to poor outcomes, including killing the tree. Too much water without sufficient aeration and drainage can have the same result.

A quick, easy way to test is to use a screwdriver to get about 2 – 3 inches down into the soil. If that soil feels moist to the touch, it’s exactly how it should be. If it’s dry, then it’s time to water.

Watering a young tree (<25 years old) is a matter of watering the roots around the trunk. You don’t want to flood the tree trunk, nor do you want to water outside the root ball.

Older trees (>25 years or a trunk over 12” in diameter) require deep watering completed occasionally. You’re looking at about 10 gallons per 1” of trunk diameter per week during dry conditions.

So how do you get that water to your trees, without standing around with a hose all day?

There is a range of solutions, from slow-release water bags, bubbler hoses, and overhead irrigation systems, through to a 5-gallon bucket with holes drilled in the base.

Citygreen has shown exceptional outcomes with the healthy and fast growth of trees by combining soil vault systems, such as Stratavault, with perforated flexible piping systems around the root ball, for example, the Snorkil products.

By creating space for adequate aeration with the Stratavault, you can limit excessive soil compression, and the perforated pipes provide airflow and enable water to be piped directly into the roots.

Combining systems like these in urban areas with permeable pavements, and connecting roof water systems to tree pits helps harvest stormwater, better managing both tree watering needs and stormwater management. To find out more about watering and aerating tree pits to improve growth outcomes, head to


How Will Cities Change Post Lockdown?

Lockdown. A time when many of us became all too familiar with our own homes. With restrictions easing in many parts of the world, many cities are re-evaluating what public space looks like.

One measure gaining traction with many businesses and local councils is the encouragement of alfresco dining and drinking. The Clematis Streetscape Project, currently in its final stage, saw one of the most iconic streets in West Palm Beach undergo significant changes, creating a more welcoming, comfortable outdoor experience.

(You can find out more about that project, which Citygreen were proud to be involved with here – Clematis Street case study)

Liverpool is another city looking to create green spaces which spread people out and improve social distancing, without resorting to bright yellow and orange ‘caution’ tape.

Their outdoor dining initiative is designed to give the city’s restaurants a much-needed boost and involves pedestrianizing several streets completely and introducing “parklets”.

According to design consultancy Meristem, parklets are a way of converting parking spaces into something far more welcoming than the typical park bench, with seating, plants, green walls, and shade trees. Where before, parking availability was a primary concern, the focus is now on creating spaces that welcome people.

Meristem director Habib Khan said, “research shows that the majority of money spent in businesses on High Streets and in cities is not from drivers anymore.” Parklets and similar spaces are a critical component of creating safe, inviting outdoor dining environments and helping businesses emerge from their coronavirus lockdown.

The use of plants and trees to provide shade and tranquillity in busy city hubs is vital, and Liverpool has even included transparent screens in parklet designs so that people can be together, but be assured in their own bubble.

And while 2016 saw office spaces everywhere looking at including green walls in their building, bringing the outdoors inside, 2020 might see the world flip the switch on that concept. With more cities looking to increase alfresco dining options, green walls and parklets might see more of our indoors showing up outside.

Citygreen is supportive of any idea that transforms grey spaces into green and helps cities and industries thrive in a post lockdown world. To find out more about our Green Wall solutions, head to

Recycling is in our DNA at Citygreen

More than 80% of marine litter is plastic, with single-use plastics making up 70% of all ocean waste. Statistics like these contributed to the recent announcement that Germany would be banning single-use plastics nationwide from July 3, 2021.

‘With today’s cabinet decision, we are taking an important national step in the fight against the plastic flood.’ Environment Minister Svenja Schulze said.

The German announcement brings it in line with the ‘Single-Use Plastics Directive’, a European Union mission to reduce plastic waste. That directive is on track to reduce the European Unions environmental damage bill by €22 billion (over $36 billion AUD) by 2030. Globally, the focus on reducing plastic waste is growing, not just through recycling but cutting the introduction of virgin plastics. Louise Edge, senior plastics campaigner at Greenpeace UK believes that companies and governments need to drive change.

‘Companies and governments still need to step up and shift us away from using plastic for throwaway items like food and drink packaging. They can ensure plastic is only used for essential items – like medical kit – and that it is captured and reused at the end of its life. That’s the only way we will stop this contamination of our environment.’

At Citygreen, recycling is in our DNA and we’re proud of our focus on environmentally sustainable systems which result in over a million kilograms of plastic being recycled and reused every year to promote healthy tree canopies in urban areas.

We take that recycled plastic and use it to make the strongest soil vaults in the world, the Stratavault and Stratacell products which are proven to improve the growth rate and health of trees in urban areas. The combination of product quality, durability, speed of installation, and 100% recycled plastics means we provide the greenest way to create green spaces.



Philadelphia launches 10-Year Urban Forest Plan

Philadelphia’s urban forest is dwindling fast, with the city losing an alarming equivalent of 1000 football fields worth of leafy shade in the last 10 years. Recognising this concerning trend, the city has launched a 10-Year Urban Forest Plan, kicking off with a ‘Tree Summit’ at the Discovery Centre in East Fairmount Park. The summit will bring together arborists, educators and community leaders organised by Philadelphia Parks and Recreation and the Office of Sustainability.

The announcement comes on the heels of a decade-long look at how the tree canopy — a measurement of the layers of leaves, branches, and stems trees provide — fared from 2008 to 2018. Overall, the report found that the city gained 1,980 acres of tree canopy in the 10 years studied, but also lost 3,075 acres. Much of the loss came from the removal of trees that line streets. Tree canopy now covers only about 20% of land within the city, the report states. The goal is to increase that to 30%.

“We’re trying to target areas that have the most need for trees and are the most vulnerable,” said Erica Smith-Fichman, Philadelphia’s Community Forestry Manager. Mayor Jim Kenney said in a statement, “The launch of the Future of the Urban Forest planning process is an opportunity to accelerate efforts from across Philadelphia to protect our tree canopy and improve quality of life and health outcomes for residents.”


Skyline of Philadelphia, PA, USA


Urban heat islands impact Adelaide’s most vulnerable residents

South Australia is notoriously hot but some parts of Adelaide are sweltering more than ever. Not surprisingly, these are the suburbs that contain “urban heat islands” leading to higher than average temperatures compared to neighbouring suburbs. You may think what difference does a few degrees make? Well, as it turns out, a lot – with these suburbs often coinciding with higher levels of vulnerability, including illness and death, especially amongst the elderly.

Former aged care worker Wendy Farmilo, 75, lives in Tranmere near Campbelltown in suburban Adelaide — an area overrun with urban heat islands. Ms Farmilo said because of cooling measures she has put in place she has managed to avoid the full brunt of the weather but is urging others to take precautions. “Older people do not drink enough water, they get dehydrated… they feel if they drink too much they might have a bladder problem,” she said.

According to a report prepared by consultancy firm Edge South Australia, nearly all of the heat islands in Ms Farmilo’s council are also home to society’s most vulnerable. “Urban heat is one of the biggest killers of people in our community, more so than any other natural hazard,” Edge SA General Manager Dr Mark Siebentritt said. “One of the big strategies we can use to tackle that is the planting of more trees. Councils right around South Australia are planting more trees than ever before.”

Landscape Architect and green space advocate Daniel Bennett said boosting tree cover would reduce heat, as well as improving “mental and physical wellbeing. Increasing the city’s connected tree canopy is one way to achieve a reduction in local temperatures as well as reducing the urban heat island effect.”

One thing is clear – as temperatures continue to soar, urban trees are not just a nice-to-have. They’re literally a matter of life and death.


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