Urban Tree Growth Unlocked:...

case study new Urban Tree Growth Citygreen

A comparison of 10-year urban tree growth with two different planting methods planted at the same time and at the same location

Key Facts

Bulcock St, Caloundra QLD, Australia

June 2011

Sunshine Coast Regional Council

Dig-It Landscapes

Elaeocarpus obovartus (quandong – 200l)

About the Project

In 1917, Bulcock Street was established as the main street of sunny Caloundra on the Sunshine Coast. One hundred years later, competing against new urban centres, big-box malls and online retail, the rundown street was in decline. In a $12 million four-stage project, Sunshine Coast Council (SCC) transformed the tired main street into a vibrant and liveable community space through the Bulcock Street Revitalisation Project. This project is Australia’s first smart city streetscape demonstration and testing facility, showcasing the latest smart city technologies.

Sian Crawford, the Landscape Architect at SCC, said, “With the Sunshine Coast Council’s Landscape Architects acting in many roles; the client, the project manager, design lead, and project delivery, our challenge was to take the community and organisation on a journey to re-imagine the high street experience through a holistic place-making framework. As Landscape Architects, we listened, learned and shaped the streetscape forms, layout, infrastructure, selected materials and plants species, and collaborated with engineers and artists, as key participants in this process of collective leadership.”

10 Year Timelapse

The above timelapse shows the canopy difference of the same tree species planted at the same time. The only difference? Increased soil volume and quality. 

A good analogy is imagine you're sitting down for dinner and the server brings you your plate and the plate is is 80% rocks. That's what trees planted in structural soil get; out of the available space, 80% is needed to keep the structural integrity of surrounding infrastructure and the tree is left over with a measly 20%; the growth and results of the tree are tied to the amount of resources available to it underground.

So, increasing the soil volume and nutrients available to the tree increases the growth rate of the tree. But that is tough to do in urban environments where infrastructure such as streets, roads, pavements, sewerage, power cables, etc take up a significant portion of underground space. This limitation will stunts the growth potential of urban trees, limiting the environmental, economic, and health benefits trees bring. However, employing innovative solutions like Stratavault will substantially enhance the available rooting area for trees by over 90%.

This revolutionary approach ensures that trees receive a more significant share of resources, promoting healthier and more vigorous growth while maintaining the structural integrity of urban infrastructure.

the difference in soil volume in structural soil vs a soil vault

The difference in space available to the tree.


Download our Stratavault Tech Sheet to understand how we grow better trees in urban environments

Project Goals

Whilst the design responded to the community’s desire for a green street with substantial tree planting and garden areas, the Sunshine City Council was also looking to build a greener and more sustainable town centre. Items that were taken into consideration during the design process included the ability to make the project sustainable in the long term with little to no human interaction.

As such, Citygreen’s Stratavault system, specialist soil mixes, and tree grow-on contracts were utilised in the building out of the project. What stands out about the systems that were put in place is their ability to ensure long-term sustainability for the project.

The capacity to deliver on the promise of long-term sustainability is Stratavault’s ability to harvest rainwater. Meaning not only do the trees take in water during a wet period, but the system is also able to collect and store the water for dry periods.

Therefore, the 35 Elaeocarpus Obovatus that were installed between 2016 and 2018, utilising the Stratavault system can continue to grow and thrive in their environment due to the council’s foresight in installing systems that look after the tree growth at the time of installation as well as into the future.

Project Outcome

“Feedback from the community has been overwhelmingly positive. In terms of the physical outcome, Bulcock Street is now a vibrantly-green, comfortable place to be. Momentum following the streetscape has resulted in a community embracing innovation and activation, with an increased sense of identity and self-determination. Eclectic in character, fun and colourful, the street has evolved into an ‘alternative’ retail experience that appeals to all ages and is unique ‘Caloundra’. Retail outcomes support this, with Caloundra experiencing an increase in the total spending during the 2017/18 financial year of 8% above the 2016/17 results (equating to $39.3 million in extra trade). An overwhelming success, the project was nominated for the 2020 Queensland AILA Landscape Architecture Awards.”, said Sian Crawford.

Images below show the results from the Council’s initial trial – where the same species of trees were planted at the same time, in the same street – with the Citygreen structural vault system (on the left), and with a rock-soil ‘structural soil’ mix, on the right.

case study new9 2 Urban Tree Growth Citygreen
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"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!"

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