There are almost 100,000 street trees across the City and our verges have room for about 100,000 more.
The City plants on average 5,000 new street trees each year through a range of programs. By 2035 our verges will be full and there will be at least one tree on each and every verge in the City.
Find out more about the Citys tree planting initiatives here.
Consistency between trees along a street results in the most aesthetically pleasing streetscapes, increases property values, defines the character of the area, and saves money through management efficiencies.
It is important to remember that street trees are part of the streetscape and not a part of the individual landscaping of each property.
Tree species diversity refers to all the different species of trees that make up an area.
Having a sufficiently diverse Urban Forest increases its resilience - it safeguards it against pests, diseases and climate change into the future.
The more closely related trees are, the more likely it is that they will all be affected similarly by any one disease, pest or environmental change. Catastrophic tree losses have happened in the past (see Dutch Elm Disease) and may happen in the future due to threats such as Myrtle Rust and Climate Change.
It’s akin to ‘not putting all the eggs in one basket’.
There are close to 100,000 street trees in the City, with over 75% represented by only 10 genera In many of our suburbs, more than 20% of all mature street trees belong to a single species.
Our Urban Forest should have a tree species diversity that makes it resilient to pests, diseases, and climate change.
For decades, municipalities across the globe have measured species diversity as the proportion of species, genera and families at a given time.
Internationally accepted standards are:
- No more than 5-10% for any given species
- No more than 20% for any given genus
- No more than 30% for any given family.
The ideal tree species diversity cannot be reached overnight. It will require deciding now what tree species to plant in each street.
We will then use the selected species to plant the gaps in the streetscape and to replace any trees that reach the end of their natural life.
In time, there will be a consistent avenue of trees.
Selecting the tree species for a street is a complicated process that considers several factors. These are listed below:
- Diversity at the suburb level and Citywide Certain species of trees may be too heavily represented in each suburb or Citywide while others may be underrepresented (see ‘What is tree species diversity and why is it important’). Preference will be given to suitable tree species that are underrepresented
- Broad environmental factors Soil types and exposure to coastal winds vary across the City and will determine what tree species may be appropriate for an area
- Cultural context and wildlife connectivity Cultural heritage and character of the area, as well as potential for creating connections between patches of habitat for wildlife are considered at this point, further restricting the number of species suitable for a particular street
- Street topologies Streets are classified based on their verge widths into 4 categories (see ‘What is the City’s vision for my street’) as this will determine the size of trees that a given street will be able to accommodate
- Street specific characteristics Presence of powerlines, footpath, existing street trees, street orientation, building setbacks.
In the process, each of the factors above is considered in order using a Tree Selection Matrix that helps officers filter out a list of tree choices to use in each location. Arboricultural knowledge is then used select a single species.
The City’s streets have been classified into 4 street types or street topologies as this will determine the size of the trees that they will be able to accommodate and the distance between them. The street topology categories are:
- Small – verge widths under 1m. These streets will be assessed on a case by case basis for planting due to their small size. Heights of trees selected for these locations will range between 4m and 10m.
- Small medium – verge widths between 1m and 4.5m. Trees selected for these locations will have heights ranging from 3 to 15m.
- Medium large – verge widths between 4.5m and 6.5m. Heights of trees selected for these locations will range between 5 to 20m in height.
- Large – verge widths greater than 6.5m. These streets will be assessed on a case by case basis for planting and may include more than one row of trees on each verge. Trees selected for this category will range between 7m and 20m in height.
Pictures of what the different street topologies look like before and after planting can be viewed here.
Verges are constrained by a paved road, a property line, driveways and, in some cases, powerlines, and often, the original soil has been replaced by clean fill. These characteristics make verges unsuitable for the majority of native trees. Only a handful of local native trees can thrive in these conditions.
Therefore non-native tree species are essential to ensuring adequate diversity and resilience of our Urban Forest.
We also have to consider that there are some residents in the City that have a strong aversion towards native trees.
Native trees are an important component of the Urban Forest. They provide shelter and food for native wildlife and are essential to maintaining our connection to Country.
We also have to consider that there are some residents who would prefer for the City to plant ONLY native trees.
Brush Box currently make up more than 15% of the street tree population, which far exceeds the ideal 5-10% for any given species. The reason is that this species is a proven performer in the hostile verge environment, not only in Perth, but also in other cities around the world, and was therefore planted heavily in the 1940’s through to the 1980’s.
As a thriving Urban Forest needs to include an adequate tree species and age diversity, the City has reduced the proportion of Brush Box planted each year. They are only planted in streets where they make up the predominant theme as it will ensure a tried and tested species continues to be utilised while also maintaining the cultural heritage of those streets.
In streets without a theme, Brush Box are progressively being replaced by other tree species as they reach the end of their lives.
The services trees provide are directly related to how much leaf surface area they have.
Bigger trees will have more leaves and provide greater benefits to the community.
The City prunes street trees annually to lift canopy height above footpaths, maintain lines of sight for vehicles, and provide clearance from infrastructure and power lines.
Trees growing under power lines are sometimes also pruned by Western Power to increase the clearance between the tree and the power lines.
Find out when your street is due for street tree pruning below:
Street tree pruning schedule
Residents are not permitted to prune street trees, instead, residents who believe a street tree requires pruning can submit a request for the City to inspect the tree and carry out any works required.
The City does not prune street trees for any of the following reasons:
- To reduce its size
- To reduce shade
- To reduce leaf/flower/seed drop
- To reduce birds nesting or feeding in the tree
- To improve views.
Residents concerned about the health of a street tree should contact the City as soon as possible to request the tree is inspected using the customer enquiry form.
Residents can help street trees to survive and thrive by:
- Giving the tree a deep watering once per week in the middle of summer
- Avoiding compaction of the trees roots by not parking on the verge.
Pruning, damaging, poisoning and removing a street tree is considered vandalism and penalties apply.
If you notice vandalism of a street tree occurring, please:
- Take photographs or video footage on your mobile phone if possible
- Call City Security on 1300 365 356 if the vandalism is currently occurring
- Report the vandalism to the City via customer enquiry online if the vandalism has already occurred.
Streets and footpaths are swept twice each year to remove leaf, flower and seed debris dropped by street trees.
Residents who believe that their street requires additional maintenance can submit a request to the City via a customer enquiry online. An inspection will be undertaken and additional cleaning scheduled if appropriate.
Tree leaves are not litter: they contain an abundance of nutrients that are best reintegrated into the soil. If left on the ground, they will eventually break down. This applies even to Eucalypt and Brush Box leaves.
Therefore, what to do with fallen leaves is a personal choice. Some options are:
- Leaving them to break down on the ground
- Collecting them with a rotary mower when mowing the grass and either composting them or placing them in the green bin
- Raking them and using them to mulch garden beds, composting them, making leaf mould or putting them in the green bin
- Using them for crafts or to play.