Street tree master plan 2023

Factors influencing tree selection and placement in these areas include:

• heavily used pedestrian zones and usually fully paved environments
• severe competition for above and below ground space and access to adequate soil volumes due to services, driveway entries, awnings, underground structures and tunnels
• the need to maintain clear sight lines to signage, traffic lights, pedestrian crossings, bus stops
• heavy overshadowing from tall buildings
• extreme wind tunnelling and downdrafts from tall buildings
• the need to maintain adequate clearances for bus and truck movements, even very close to footpaths.

Factors influencing tree selection and placement in these areas include:

• often very narrow fully paved footpaths
• narrow streets or streets that have been converted to increase car parking availability
• competition for above and below ground space and access to adequate soil volumes due to services, driveway entries, and overhead power lines
• minimal setbacks to adjoining buildings
• the need to maintain adequate solar access to adjoining residential premises.

Factors influencing tree selections and placement in these areas include: 

• often wider streets that need to accommodate large trucks and kerbside car parking
• severe competition for space due to major services and large driveway entries
• more generous footpaths, often with grass and narrow pedestrian paths offering good opportunities for tree planting
• overhead powerlines usually present on one side of the street
• variable setback conditions, but often with very good setbacks to the adjoining buildings.

Although not common in our local area, these areas are often in the more favourable sandy soil conditions, with factors influencing the tree selections and placement being:

• often lower traffic volumes and wider streets
• more generous footpaths, often with a grassed verge strip and a narrow pedestrian path offering good opportunities for tree planting
• overhead powerlines but usually present on only one side of the street
• good setbacks to adjoining buildings.

Due to the age and style of development throughout much of the inner city, and older terrace housing areas, our area has many narrow laneways. These are often very narrow streets that are dominated by parking and access to adjoining shops, businesses and residential properties. They usually have very little planned tree planting. Trees that are in such laneways are often trees that may have been planted or fostered by well-intentioned residents but may not be entirely appropriate for their location.

We recognise laneways offer spaces to enhance our urban greening and we have considered the potential of all laneways as part of this Street Tree Master Plan.  With carefully planned traffic island planting and adjustments to parking, useful trees can be introduced and make a valuable contribution to our canopy cover, summer shading, biodiversity and urban heat mitigation.

Tree size – The trees selected will be in scale with the streetscape, and where appropriate we will always use the largest growing species possible for the space available. Very large trees within confined spaces often result in unacceptably high management costs and infrastructure and property damage. Conversely, small growing trees in broad streets rarely contribute significantly to visual quality of the street or vital canopy cover. 

Species should still be selected to ensure the ultimate mature size of the tree is in scale with the street giving consideration to the relevant constraints, such as footpath and nature strip widths, overhead powerlines, building setbacks and vehicle clearances. The optimum range is a tree that is not too small that it fails to make a contribution to the amenity of the street, and not so large it dominates and causes significant problems. In some instances, the constraints imposed by the street environment will limit the size of street tree selected or even restrict tree planting altogether. This is frequently the case with the majority of our very narrow laneways and footpaths.

This plan now nominates ‘constrained’ species in many locations to help further guide the selection of a smaller growing tree where specific circumstances may limit the otherwise preferred street trees.

Tree form – Street tree species should have an appropriate and predictable form, usually with an upright trunk with spreading and stable branch structures. Street trees need to have a form that allows traffic and pedestrian movements around and under the tree. In the city centre, in particular, desirable tree forms include trees with a single straight main trunk that supports a domed crown, or in some locations with narrow columnar forms.

The capacity of a tree to establish and grow successfully depends on the environmental conditions at the planting location being within the tolerance range of the species selected. The underlying geology and soil provides access to nutrients and water as well as physical support for the tree. Soils can differ greatly in terms of their available nutrients they provide, their drainage characteristics, oxygenation and depths.

The western part of our local area, including Chippendale, St Peters, Erskineville, Newtown and parts of Glebe are situated overlying Wianamatta shales which usually produce heavy clay soils with moderate fertility and higher water holding capacity.

In Pyrmont and Ultimo and on the eastern side of the city in areas such as Woolloomooloo, Darlinghurst and Surry Hills the underlying geology is Hawkesbury sandstones which typically produce very shallow, sandy, and low nutrient soils.

The southern areas from Moore Park to Rosebery are situated on ancient dune sands which have been blown inland from the coast. These soils consist of relatively nutrient poor soils, but they are typically deep and well drained sandy profiles, and can present very good conditions for tree planting and growth.

Many areas throughout the City of Sydney area are also highly disturbed and the original soils have been completely removed and replaced with imported fill, often including rubble, building debris and other unnatural landfill materials. This is particularly common around the harbour foreshore and older industrial areas.

All street trees, by their position and nature, may interact and conflict with kerbs, pavements and services. Correct placement, providing adequate soil volumes, creating suitable pavement openings and choosing appropriately sized trees is all important. Trees are chosen to ensure the size and spread of their root systems is compatible with the space available. The City of Sydney also investigates the use of alternative footpath materials and other designs to help minimise tree root and infrastructure conflicts.

Proven performance of the species under the current and future environmental conditions of the precinct is vitally important. Trees are a very long-term investment and substantial amounts of money are often invested in their purchase, planting and maintenance. New species should and will be trialled in limited locations before implementing their more widespread use. If a trialled species does not perform as expected, an alternative species with similar attributes (such as mature size, evergreen/deciduous, form) will be used.

About the climatic conditions, Sydney is located on the south-east coast of Australia and enjoys a moderate (temperate) climate. It generally escapes the extremes of temperatures common in the interior of the continent and the very high humidity of the more tropical coastal areas. It generally experiences a warm and wet summer and autumn and then a cool and drier winter and spring. Mean daily maximum temperatures (25°C) occur between December and March with mean daily minimum (<10°C) between June and August. The street trees selected must be able to thrive in both our current and our predicted future climatic conditions.

It is also important to consider the microclimatic conditions that present in a particular location. In the city centre and high-rise inner city areas experience overshadowing caused by tall buildings, wind tunnel effects and reflected and re-radiated heat that require tree species that are particularly hardy and resilient to these adverse conditions.

The street tree species palette includes both evergreen and deciduous trees, which differ in the type and quality of the shade they cast. Evergreen species provide all year screening, greenery and shelter from winds. Deciduous trees provide seasonal interest while maximising winter light. In residential areas and some city centre streets deciduous trees are extremely useful to maximise summer shading and winter light, particularly for footpaths and buildings located in east-west oriented streets.

The foliage size and colour of tree leaves may also influence the visual texture and aesthetics of a streetscape. 

The selection of species may have natural, historical or cultural associations in a particular street or precinct. Tree selection should consider the historical context of the precinct. Many areas such as Glebe, Potts Point, Darlinghurst, Newtown, Surry Hills and Chippendale contain intact period architecture, particularly from the Victorian era. If appropriate, street trees are chosen to be sympathetic to the heritage values of the surrounding built environment to further strengthen the sense of place for these areas.

Many of the costs associated with managing trees in an urban environment are associated with the early establishment and then the ageing phase and removal of the tree. Using longer lived tree species that require less frequent replacements help minimise tree management costs and maximise tree related benefits.

The selected tree species should be resistant to foreseeable pests and disease. A greater diversity of species across the city is important in reducing the potential impact of any future devastating diseases that may impact a specific tree species.

Limb loss may occur on an occasional basis for most trees due to age or to wind and storm breakage. Trees that are renowned for having particularly brittle branches, poor branch attachments and regularly known for sudden failure of larger limbs will be avoided for use as street trees.

The city environment and areas close to busy arterial roads are subject to higher levels of photochemical pollution that is expelled from vehicle exhausts. Trees selected for these areas need to be able to tolerate these vehicle emissions and pollutants.

Deciduous trees are generally considerably more tolerant than evergreen species due to the duration over which different species retain their leaves. The longer the life of a leaf the greater the likelihood that the threshold levels for pollutant damage will be exceeded.

Tree species are selected to minimise maintenance once they have become established. Trees that require excessive ongoing maintenance, repeated pruning, or pest and disease control are typically avoided.

It is a natural function of all trees to shed leaves, fruit or bark to some degree. In urban settings this is usually easily managed through routine maintenance of the surrounding area. The selected tree species must have an acceptable level of maintenance associated with it and suited to the surrounding location. Trees with large or heavy seed pods, excessive leaf drop, hard and round fruits, or fleshy fruits or flowers which may lead to slip and fall hazards are typically avoided.

The selected trees must be capable of being commercially grown and available in a suitable size for planting in streets. Generally, the tree nursery stock that will be used for our streets are super advanced stock to provide suitable visual impact and the adequate resistance to casual damage or intentional vandalism.

Some species are known to be, or have the potential to be, serious environmental weeds due to their ability to self-propagate and invade bushland areas. Those with known propensity for this within the Sydney and urban context are avoided.

Trees provide shelter, food and other habitat resources for a range of fauna species, including small mammals, birds, reptiles and insects. Wherever possible, consideration has been given to planting trees which expand and provide a connection between open spaces or other vegetated areas. Particularly those identified as priority habitat areas in the City of Sydney’s Urban Ecology Strategic Action Plan, to increase the area of available habitat and assist in the movement of native fauna between those areas. Although native trees are preferable in this regard, exotic species also have some habitat value. A mix of species are used where appropriate.

Sydney’s natural landscape has changed dramatically. In the past 220 years, we have altered the soils, the way water moves and displaced ecological systems. Ecosystem health and biodiversity is important for a sustainable world. Protecting and improving urban biodiversity, while also reclaiming and managing functional ecosystem health in the city, can play a vital role in improving community health and wellbeing and the liveability of the city. 

Street trees are an important part of our wider urban forest and can provide valuable and linked corridors of vegetation and canopy that can promote and enhance native habitat and provide sources of food, shelter and other benefits for our native birds, animals, insects and other creatures. Well planted and shady streets can provide important respite and corridors for the movement of species. This can be particularly important for bees and other insects that may not be able to fly large distances in more open or exposed areas.

We have planned and initiated longer term reductions in the use of some street tree species in certain areas, where we have identified historical over reliance on one or two species, such as of London plane trees (Platanus x acerifolia) in our northern suburbs, and broadleaf paperbarks (Melaleuca quinquenervia) in our southern suburbs.

We are also planning to introduce far more trees into our streets, including some streets that have never had trees, such as smaller laneways and other smaller streets. We are planning to achieve this through increased use of in-road planting initiatives and continued adoption of under grounding of powerlines and converting key streets to aerial bundled cables. We have also aimed to increase the use of more locally indigenous species. The combination of these initiatives and our continued goal to increase urban greening generally will allow our streets to improve ecological connections and provide useful steeping stones for our native urban fauna, particularly between major parklands such as Sydney Park, Moore Park, Jubilee Park and The Domain and other harbour foreshores. 

We have focused on exploring and selecting some trees species that are expected to be more resilient to the forecast impacts of climate, thereby providing greater resilience for our tree canopy and urban forest, particularly in times of droughts, heatwaves and generally warmer climate scenarios.

The trialling of new and lesser-proven species will generally be undertaken on less prominent local streets and laneways. They will be closely monitored for performance and suitability in the years following their installation. Trialling new species is an important way to identify and assess trees that may contribute to our key objectives into the future.

However, trialling new species also has challenges. The commercial availability of such species can pose difficulties in sourcing adequate trees in the required sizes and numbers and at the times required. If the trial species fails to thrive in our conditions or is susceptible to unexpected pests or diseases then the wider use of that particular species may be limited to only more optimised sites or abandoned altogether. If a trialled species does not perform as expected, an alternative species with similar attributes (such as mature size, evergreen/deciduous, form) will be substituted.

International precedents show that widespread infestations of serious and harmful pests and diseases can have devastating consequences on parts of our urban tree populations.

There are several major pest and disease threats that may impact the trees in the City of Sydney area. These are typically introduced pests and diseases that can potentially have devastating impacts on certain species of trees. Specifically, these include pests such as:

Phytophthora root rot

Phytophthora root rot (Phytophthora sp.) is a serious microscopic plant pathogen that infects and kills a broad range of tree species and is widespread in many of our urban environments. It is spread mainly by movement of infested soil, roots, plant material and free soil water. Any activity that moves soil, water or plant material can spread this pathogen. This includes soil in new plants, on tools, footwear and vehicles.

Phytophthora is now increasingly common in the landscape, across large portions of the country. It is responsible for extensive tree death and decline. There are no effective treatments. Once plants are infected decline is typically rapid. Phytophthora destroys the ability of a plant to take up water from the soil, often leading to catastrophic wilting, foliage collapse, and then death of the tree. The progression of the disease is highly species specific, with some trees able to withstand the affects for several years with only minor symptoms, while others can be killed within a very short period.

The best defence against the disease is maintaining healthy trees and promoting healthy soils that possess numerous naturally occurring and often competing fungi and microbes, helping to keep the balance of microbes and may even prey on the Phytophthora itself.

Sycamore lace bug

Sycamore lace bug (Corythucha ciliata) is an insect pest introduced from North America that mostly affects London plane trees. It was most probably introduced to NSW in 2006 and prefers to feed on London plane trees (Platanus x acerifolia). The tiny adults and nymphs feed on the underside of the leaves, causing bronzing, chlorosis and premature leaf drop. Severe infestations can cause complete defoliation. Several consecutive years of infestation may kill affected trees. Control is difficult and expensive.

It is now widespread in the Sydney basin and evidence suggests it is spreading along major transport routes. Establishment of younger trees in affected areas is proving to be particularly difficult. 

The ultimate effect of this pest on Sydney's plane tree population is still evolving but attempts have been made in this plan to greatly reduce the reliance on plane trees while treatments such as insecticide injections are used on affected trees to maintain their health and longevity.

Myrtle rust

Myrtle rust (Uredo rangelii) is a particularly serious fungal disease native to South America. It was first detected in Australia on the Central Coast of NSW in April 2010. This fungus can affect plants belonging to the family Myrtaceae which includes many of the very common native species such as eucalypts, paperbarks, myrtles, lilly pillys, bottlebrush and water gums. These trees continue to represent a very large proportion of the City of Sydney's street trees and surrounding native vegetation communities. 

It is easily spread and the NSW Department of Agriculture, Fisheries and Forestry has now advised it does not believe the disease can be effectively contained or eradicated. It has been listed as a key threatening process under the NSW Biodiversity Conservation Act 2009.

When severely infected, young plants and new growth may become stunted and in worst case the plant may die. Little is currently known about the disease and its impacts to plants under Australian conditions. Treatment using various fungicides may be possible, but this will usually prove unviable on large trees in public areas. Control will only apply to small plants and controlled nursery environments and the like. The ultimate effect of this disease is still not known. Tree species known to be highly susceptible to myrtle rust have not been selected for use in this plan.

Fusarium wilt

Fusarium wilt, caused by the fungus Fusarium oxysporum, is a devastating disease of certain species of palms, including Phoenix and Washingtonia. Fusarium Wilt has been observed at many locations in Sydney, including in the City of Sydney’s parks. 

The fungus causes a vascular wilt, obstructing the water-conducting tissue, which results in desiccation and death of the fronds. The fungus produces short and long-lived spores that can live in the soil and plant tissue for long periods, usually years. Because most of the root system is left behind after a palm dies from this disease, this mass of roots may act as a reservoir for the fungus for a long time.

The disease symptoms normally appear first on the oldest (lowest) living leaves, and then progressively move upward in the canopy until the palm is killed. Transmission of the fungus from palm to palm is mainly through contaminated pruning tools. Once a palm is infected it usually ultimately dies. 

Most significant of all factors that limit the benefits trees can contribute to a streetscape is the conflict between overhead power cables and tree canopies in our older and more established suburbs. We have been proactively coordinating with Ausgrid in the continued installation of aerial bundled cables. These consist of several insulated wires bundled into a single cable, eliminating the need for the wide strung powerlines that conflict with tree growth. These cables also allow for reduced pruning clearance requirements resulting in less impact on tree canopies. To maximise the benefits from these cables, we may review existing trees and the nominated species within this plan.

An alternative solution to this problem is to select smaller tree species. This is often viable for very narrow streets, however in wide streets small trees are inevitably out of scale with the streetscape and present a poor environmental, social and aesthetic outcome.

Underground power cables are also an option, particularly for new developments such as at Green Square, Zetland and Alexandria. Most new developments allow the undergrounding of power and allow for the unrestricted adoption of larger trees and lower ongoing maintenance costs. In established areas, the cost of undergrounding existing powerlines is often prohibitive and difficult to manage around the roots of existing mature trees.

An important factor in species selection is the width of the footpath or verge that is available planting. Trees planted in footpaths less than 1300mm wide (from the building line to the back of the kerb) force pedestrians, particularly those with strollers, walking aids or using wheelchairs, to divert onto the road. As it is safer to encourage pedestrians to stay on the footpath, trees will therefore not be planted in any footpaths less than 1300mm in width.

In streets with footpaths less than 1300mm that already have tree planting, no new tree planting will be undertaken. However, in-road planting or creating ‘shared zone’ pedestrian options can be explored to install new or additional trees.

Locally indigenous trees have had the advantage of evolving to our local climate. They have evolved in harmony with naturally occurring organisms such as insects and fungi. Their use can promote biodiversity and creation of wildlife corridors, reinforcing a local sense of place, connection with Country. 

Locally indigenous species are often highly adapted to bushfires and as a consequence they have a natural tendency to have vigorous growth for brief periods after fires when soil nutrients are temporarily higher and they race to re-establish a forest canopy. When these trees are grown in an urban environment that is free of fires and high in nutrients they may become very elongated, structurally weak and the foliage and bark may become more susceptible to attack by insects and other pests.

Many of the familiar natives such as eucalypt trees are often very large trees that are unsuited to planting in smaller streets and close to buildings. They often originate from open and much drier vegetation communities with impoverished soils. These species often perform poorly as street trees, within inner urban areas, due to their more specialised physiology.  They are often adapted to soils of very low nutrient status and with perfect drainage where they are less susceptible to pathogens. Soils in our streets often have vastly different properties, and often these species don’t thrive.

An important advantage of many exotic species, in an inner urban context, is that they include most of the useful and proven deciduous trees that can provide solar access to the streets and houses during winter. There are very few natives that are deciduous, and generally those that are lose their leaves in spring or early summer (an inheritance of their more monsoonal origins). Red cedars and white cedars (Toona ciliata and Melia azedarach) are native trees that have winter deciduous attributes, but both suffer from severe pest problems under urban conditions and are usually unreliable performers.

Many exotic deciduous species have the advantage of decades, if not hundreds of years of selective breeding which ensures improved reliability. They are usually pollution tolerant, often demonstrate greater resilience to interference with their roots or damage during construction works. The canopy shape and branching architecture of many exotic trees are also able to tolerate the pruning and shaping required for urban environments.

In summary both natives and exotics have their strengths and weaknesses for use as street trees. This plan aims to plant the right tree for the right place, for the right reason and strike an appropriate balance between native and non-native species.

A key feature of our local area is the harbour foreshore that extends from Rushcutters Bay to Glebe and Blackwattle Bay.

A principle that has been reinforced in this plan is to establish, where appropriate, native figs and palm trees and other endemic trees such as the Sydney red gum (Angophora costata), red bloodwood (Corymbia gummifera) and cheese tree (Glochidion ferdninandi) along the streets running towards and adjoining the foreshore. This will provide a stronger definition, return of a native character and a greater ‘sense of place’ of the original harbour edge. Palm trees will often be used in clusters or in more formal avenues to identify key nodes without blocking some important views to the harbour and historic buildings.

Many of the City of Sydney's parks, such as Hyde Park, Redfern Park, Prince Alfred Park and Victoria Park have large trees, remaining from early Victorian period planting. These large and prominent tree canopies frequently extend well over the adjoining streets. The planting of street trees along these streets is often avoided to minimise canopy conflicts. This also allows the park and its major trees along the park edges to remain a feature of the street. 

Where required, species should be selected that will provide an appropriate level of solar access to dwellings during winter. This is usually most important in east-west oriented streets in areas with older terrace buildings that were not well designed for passive natural light. It can also be important in high-rise apartment streets where deciduous or less dense trees can provide light to otherwise very shaded streets in winter. In meeting this objective, consideration is also given to other principles such as species diversity and the existing street characters.

Major ‘gateway’ streets include Anzac Parade, Oxford Street, William Street and Parramatta Road/Broadway. These gateways have already, or will be, further acknowledged and celebrated by public space improvements such as footpath widening, which together with continued tree planting, will create prominent and recognisable tree-lined avenues to reinforce their importance.

The state and regional roads in our area include some major connections such as Anzac Parade, George Street, Parramatta Road/Broadway, William Street, South Dowling Street, Harris Street, Botany Road, Abercrombie Street, Regent Street and Cleveland Street.

These prominent and wide streets form major vehicle or pedestrian corridors and are often considered different in character to the local streets they divide or bound. These streets are strengthened with a consistent and unified tree planting scheme, using some of the hardiest and most reliable trees.

Where this plan nominates a species for ‘both’ footpaths it is expected the species will be planted on both sides of the street. If it is determined different species are only planted on a single side, that species will have a particular orientation nominated, such as ‘north side’ or ‘south side’ only.

Where two (or more) species are nominated for ‘both sides’ this indicates the species are planted in a mixed or alternating arrangement. This allowed for the continuation of pre-existing street planting, the introduction of greater diversity, and the option for both deciduous and evergreen trees within a street

The ultimate selection of which of the species to plant may be influenced by issues such as nursery stock availability, tree size, available soil volumes and the specific characteristics of the individual planting location.

Where no footpath species are nominated, then it has been determined that the footpath cannot accommodate tree planting. This may be due to intrinsic obstructions, overhead or underground services or narrow footpath width. In some instances, it may also be due to important historic buildings or the relationship to adjoining parks.

The City of Sydney continues to identify numerous potential in-road planting sites. Using our new online street management tools we now have the ability to consider and specify the desired species that will be used for such special circumstances. These species may be different to the trees that have been otherwise specified for footpaths to ensure clearances to traffic and help us maximise canopy coverage and biodiversity.

The exact details of these planting opportunities will be dictated by more detailed design and analysis that will include assessments of drainage, available soil depths and volume, underground and overhead services, parking and traffic analysis and budget prioritisation.

In many streets with wide carriage ways, traffic islands along the edges of the road or creating central median strip plantings may both be possible options. The decision of which style of treatment is to be used will be subject to individual street and traffic assessments and more detailed consultation with the immediate local community.

The proposed species to be planted in-road will be in line with this plan unless special circumstances or unidentified design constraints dictate otherwise.

If no species is indicated, then it has been determined that in-road planting is extremely unlikely or not feasible for that street segment.