RootCells from CityGreen Systems, represented in Australia by Arborgreen Landscape Products , recently played an essential role in a Bankstown City Council streetscape and transport corridor upgrade project.
The project won first prize in the local government/public works category of the 2009 Engineering Excellence Awards of the Institute of Public Works Engineering Australia NSW (IPWEA), and also first prize in the Cement and Concrete Association of Australia (CCAA) 2009 Public Domain for Streetscape
Emily Forrest of the Sustainable Development Unit at Bankstown City Council explained, “We had been planting our new advanced trees in structural soil for two years prior to that, so we took a leap of faith. It’s definitely worked out for us. The trees that used the new system are all looking fantastic.”
The 40 trees planted using the CityGreen root protection have healthy and vibrant canopies.
The award-winning bus corridor and interchange was constructed over three years and provides an improved transport system for both local and regional bus routes. It also provided an opportunity for further improvements to the Bankstown City Plaza streetscape and other council infrastructure in the area.
CityGreen root protection system – how it works
A spokesperson for CityGreen Systems, the Australian distributor of the RootCell explained that soil compaction, insufficient drainage, lack of aeration and restrictive pavement openings are often the cause of tree planting failure in urban landscapes.
RootCell tree root systems ensure the soil has enough space, which is essential for healthy tree roots to grow into, and the strength to prevent them being compressed by traffic above or adjacent to where they are planted. This ensures that the tree roots receive vital life-giving nutrients, including water and oxygen, so that they are able to flourish in the challenging city environment.
A typical tree planting pit in the street upgrade was 1200 mm by 1200 mm by 800 mm deep, with structural RootCells buried around the root ball and a Tree Grate surrounding the tree base for protection.
Root Directors buried around the perimeter of the pit direct the growing roots into the RootCells and prevent them disrupting the pavement. A RootRain irrigation inlet is connected to buried perforated pipes that loop around the tree above the RootCell root protection system.
Vertical Tree Guards from CityGreen shield the growing trees from damage until they are large enough to stand on their own without protection from vandalism or accidents.
Tree Grates at pavement level were specifically designed with small apertures so that water was able to penetrate, but are too small for debris such as cigarette butts that might collect in the tree hole.
The Bankstown streetscape included Pyrus calleryana ‘Bradford’ (Ornamental Pear) trees, which were chosen for their broad canopy and tree shape, single trunk form, hardiness, proven performance and reddish autumn leaf colour. A 200 litre rootball was the size nominated at planting of these trees.
Also used in the streetscape were Fraxinus ‘Urbanite’ (Ash) trees, selected for their tree form and size, multi-fingered leaf shape and effect. These trees were planted in 200 litre size pots, with structural soil in between the trees.
New Sapium sebiferum (Chinese Tallowood) trees with the CityGreen root protection infrastructure will be used to replace Ash trees that were planted around 13 years ago.
A couple of Ulmus ‘Lutescens’ (Golden Elm) were chosen as accent trees in the latest streetscape upgrade because of the bright green foliage that contrasts pleasingly with the dark grey paving.
Lagerstroemia indica ‘Tuscarora’ (Crepe Myrtle) was selected for flower colour, mottled foliage and bark patterns. Andreasens Green Nursery had some magnificent specimens available in 1000 litre root size perfectly suitable for this purpose.
Corymbia maculata was chosen to provide a majestic and fast-growing native screen to the railway.
“The council now chooses deciduous trees for the commercial streetscape to create a point of difference to urban street plantings, which are predominantly native species. Deciduous trees contribute to the removal of air pollutants, which are captured in the leaves and disposed of when leaves are removed from the site.
“The trees also reduce pollution in urban runoff by filtering waterborne particles and nutrients, while entrapping dust and other air-borne particles.
“Programming for leaf litter removal can be more easily planned with deciduous trees than with natives that lose their leaves year-round. Deciduous trees that are bare in winter also let through more sunlight when it’s needed,” Ms Forrest said.
RootCell tree root protection products available from Arborgreen Landscape Products are attracting increasing attention throughout Australia and New Zealand. Many arborists and landscape architects are now recognising that the modular, structural soil cells represent current best practice for trees in cities.
The new, patented StrataCell Generation IV RootCell root protection system is strong and available globally.