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.

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

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.

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.

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.

Soil Volume Calculator

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

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.

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.

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.

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.