Better Shade Trees for Brisbane project – Riverhills

Brisbane City Council is pleased to advise of a new water-saving trial on street trees commencing in the suburb of Riverhills from June 2021. The Better Shade Trees for Brisbane project  supports the delivery of Council’s Brisbane. Clean, Green, Sustainable Strategy, which aims to achieve a 50% shade target for footpaths and bikeways in residential areas by 2031 and Council’s Greener Suburbs program. 

Project summary

About the project 

Council is pleased to advise the Better Shade Trees for Brisbane project has now commenced. The project is trialling three water-saving technologies on Brisbane street trees, with the aim of understanding how to best support street trees' growth and achieve greater shade cover in our suburbs, while also reducing reliance on street tree watering vehicles.

The trial commenced with the planting of 12 Elaeocarpus reticulatus (blueberry ash) trees in Riverhills in mid-June 2021. View the tree locations:

• Better Shade Trees for Brisbane project - trial tree locations (PDF - 155kb)
• Better Shade Trees for Brisbane project - trial tree locations (Word - 1.3Mb).

Nine of the twelve trial trees have been fitted with water-saving technology, while three of the trial trees have only had mulch applied. These three trees will act as the control group against which the health of the trees fitted with water-saving technologies will be measured.

The three water-saving technologies being trialled in this project are:

1.  The 'soak pit' which captures stormwater runoff from the road. Runoff is diverted to a gravel pit that slowly releases water into the ground for the tree to take up as needed.
2. The 'Greenwell which is a commercially available product designed to hold water and mulch around the base of the tree in a circular raised plastic guard. It has a volume of approximately 26 litres.
3. The 'TreeFrame' which is another commercially available product also designed to hold water and mulch around the base of the tree, but in a square raised plastic guard that has a capacity of approximately 100 litres.

Eight of the trial trees are fitted with monitoring devices that measure moisture levels in the soil. A metal stake may be visible adjacent to the tree housing the data transmitter. Do not interfere with this device or any of the technologies you may noticed attached to the trees, as this may impact the integrity of the trial results.

The Better Shade Trees for Brisbane project specifically targets properties with no existing kerbside trees. Preferred locations were identified prior to the program commencing based on the access, grade and location of existing street trees. The suburub of Riverhills was chosen for the trial due to the multiple planting opportunities available in close proximity and because the suburb has the necessary reception to the wireless network required by the monitoring devices. 

The trial will run intensively for two years from June 2021 to mid-2023. A final survey will be undertaken five years after the planting to determine the long-term effects of the technologies. 

The trial will assess the health of all 12 trial trees based on the:

• thickness of the trunk at breast height
• height of the tree
• health and vigour of the tree, including characteristics of its leaves such as the density and colour of foliage.

The results of the trial will inform future design and implementation strategies for Council’s street tree planting program; and the use of water-efficient technologies will be considered for both new street trees and for retrofitting on existing street trees.

Preferred locations were identified prior to the program commencing based on the access, grade and location of existing street trees. A number of factors were taken into consideration in choosing the final locations of the trial trees, such as: 

• there is adequate space (e.g. currently there are no other trees located at the front of the property)
• there is no interference with below-ground services
• the street tree is located in accordance with Council’s specified tree placement guidelines (e.g. it will not create any visual obstructions for road users or pedestrians)
• there have been no objections raised by the residents adjoining the kerbside location.

The Elaeocarpus reticulatus (blueberry ash) tree was chosen for the trial as it is a beautiful and hardy evergreen tree, which grows between 3-15 metres tall and 3-5 metres wide, and for its aesthetics and ability to attract native birds and butterflies. 

Important details to note about the trial include: 

• Qualified personnel will water, care for and monitor the trees for the full duration of the trial period. 
• The same tree species has been selected for all sites to ensure a consistent set of parameters for the trial.
• Residents are NOT required to care for the tree. As this is a project that aims to test the performance of a variety of water saving devices, it is important that each tree receives the same amount of care and attention. For this reason, Council requests residents DO NOT water or fertilise the trees, or the lawn immediately surrounding the street tree. This is a strict trial where care and maintenance will be scheduled and documented. This is to ensure all trees receive the same care which will ensure there is consistency across the trial trees and will make the results more robust. 
• Residents’ usual obligations to mow and whipper snip the areas of their properties that adjoin the kerbside will remain throughout the trial period. 
• Residents who DID NOT wish to have a tree planted on the kerbside adjoining their property had 10 days to notify Council of their desire to opt-out of the program. 
• Participation in the trial was only open to residents of Sawmill Circuit, Riverhills. However, residents from other suburbs can request to have a street tree planted at any time through Council’s street tree program. 

Project timing

The trees were planted in mid-June 2021. The trial will run intensively for two years from this date, during which time Council staff and contractors will water, fertilise, care for, and monitor the trees. From July 2023, the trees will be left to mature and will receive the same level of care that Brisbane street trees receive as part of Council's street tree program. A final survey will be undertaken in mid-2026 to determine the long-term effects of the technologies.

Project benefits

Water-saving technologies are estimated to improve tree growth and canopy cover by up to 200% within a five-year timeframe. Larger tree canopies help to reduce temperatures in the urban environment, which increases the walkability of our streets.

Other benefits of water-saving technologies include:

• enhanced street tree performance, health and resilience through enabling self-watering 
• reduced tree establishment, and ongoing maintenance and watering costs 
• removal of some pollutants (sediment/nutrients) from the stormwater prior to entering receiving waters (relevant to the 'soak pit' technology only).

More information 

If you would like to find out more about this project, you can:

• phone the project team on 1800 669 416 during business hours
• phone Council on 07 3403 8888 outside of business hours
• email the project team
• write to:
  Better Shade Trees for Brisbane project 
  City Projects Office
  Brisbane City Council
  GPO Box 1434 
  Brisbane Qld 4001.