It is widely accepted that we need more trees in our urban centres to combat the heat island effect that will only worsen due to climate change.

It’s an environmental necessity requiring unprecedented commitment from state and local governments, developers, local communities and homeowners.

A 2017 report by the Centre for Urban Research, RMIT University, found that tree canopy and shrub cover had dropped 2.1 per cent since 2013, adding to the loss recorded in the five years prior. We went backwards! 

This in part prompted the national Greener Spaces Better Places initiative and the NSW government’s five million trees by 2030, increasing Sydney’s tree canopy from 16 to 40 per cent.

The 2022 target is one million trees. How many will survive?

When it comes to trees, resilience is everything

These urban forest goals are ambitious, requiring huge investments in time, labour, tree stock and water. And, as it is with human babies, the early years are critical. 

In 2016, Sydney company, WaterUps, re-invented the age-old concept of water wicking beds. Using recycled plastic for wicking cells and perlite we sought to create sustainable solutions for improving food security, urban greening, and water management.

Initially adopted by home garden and horticultural markets WaterUps has invested in research and development, including field trials to optimise its suitability for commercial, civic and other applications. 

In 2022 the company started working with two Sydney councils on two trials: (i) Street Trees – Verge Plantings and (ii) Canopy Trees – Built Environment using our sub-irrigation channels (SICs). These enclose wicking cells in a plastic casing creating a water reservoir.

The purpose of these trials is to ascertain the optimal watering schedule for trees using the WaterUps SIC.

Planting / establishment phase

Gardens or plantings that use WaterUps require significantly less water and thus less watering – in certain applications 20 per cent of the water of top-down irrigation systems. 

In the tree planting phase, a single WaterUps SIC is placed in the ground under the sapling, providing a water capacity of 17.5 litres. A capped pipe extends above the ground to facilitate topping up of the reservoir. This in an advance on the coiled tube many councils have used in the past because it delivers an inbuilt reservoir. 

WaterUps draws water from its reservoir system that can hold 110 L for every 1 square metre. But it also provides optimal soil conditions by ensuring water is closer to where the plant needs it – the roots – thereby saving on evaporation and promoting stronger root growth. The wicking cells facilitate better soil aeration and less compaction, which is added benefit when it rains. 

Nurturing / management phase

For street trees, the NSW government recommends 10L of water be applied over the first 18 months as follows: 

  • four times per week for month 1 (16 waterings)
  • three times per week for months 2 and 3 (27 waterings)
  • two times a week for months 4 to 18 (130 waterings)

That’s 172 waterings (maintenance visits) in 18 months and 1730 litres of water per tree.

WaterUps provides the means to decrease water usage and the watering schedule while improving canopy growth. This allows for more trees to be planted and maintained, fast tracking urban forests.

Water usage

With WaterUps the 17.5 litre reservoir ensures the water lasts longer, using 70 litres, compared to 160 litres without, in the first month. Over 18 months the SICs use 787.5L compared to 1730 L. That’s a saving of 942.5 L or 54 per cent. 

Maintenance time

By being more water efficient a tree with a SIC requires 45 watering visits over its first 18 months. That’s 128 less visits and a huge saving of 74 per cent in maintenance costs.

Financial savings

These water and time savings correlate to $580 in the first 18 months of a single tree. That’s $580 million for 1 million trees! The savings continue…

Environmental savings

With the wet La Niña weather event, the reservoir system will capture rainwater, a far superior water supply. It also enables the capture of any fertilisation applied, thereby minimising the eutrophication of nutrients in our waterways.

Fast canopy growth

The biggest plus though is, by creating optimal growing conditions, saplings can grow an addition 30 per cent in canopy size each year for the first three years of their life. This is based on trials done on a variety of plants in Sydney, Tasmania and South Australia and lived experience over the past five years. 

As with most trees, the canopy size above is balanced by the root structure below. While the roots will grow beyond the WaterUps wicking SIC it will always be there to provide water immediately under the tree and to store water in periods of downpour. 

Why is this important? Because the faster a tree is established the greater its ability to sustain itself during dry spells. 

Resilient trees, diverse trees

This sustainable watering solution can be used to create more resilient trees, however, different tree species in urban communities are also needed for greater biodiversity and resilience. Monocultures increase the risk of negative impacts from drought, pest and disease. Climate change will also alter our temperate zones, so we need to factor this into tree selection.

Broad Applications for Urban Greening

Because our cities are already built up, increasing the urban forest is going to require ground works of pavements. WaterUps 1000L reservoir system will provide a lifetime water management tool for canopy trees in the built environment and our SIC can be used in rooftop gardens to create more shade.