Management of Urban Forests in Remote and Arid Environments

Deon Schumann – City of Port Augusta

Port Augusta is situated at the head of Spencer’s Gulf and is the northern most regional city in South Australia. We are the driest city in the driest state on the driest continent with an average rain fall of 250mm per year, but on many occasions this targeted rain fall is never reached.

The city has a population of approximately 13,516 residents and is known as the ‘Cross Roads of Australia’.

The council encompasses an area of approximately 1132.6 km2, with 170 Kms of sealed roads within the city limits, with 276 km’s of footpaths with approximately 30,000 street and parkland trees under our care and control. The city also has 74 parklands, 3 main turf ovals and a dirt oval under council’s care and control with shared agreements with ovals within the property boundaries of 3 of the Education Departments Schools.

The soils within the city consist mainly of clay, clay loams and red sand depending on which area of the city you are in and Stirling North consists of clay alluvial soils. All the soils in the area are alkaline with a Ph above 7

CITY GREENING

Port Augusta has a vast and diverse planting of tree species within the city under council’s care, it is amazing as to what you may find in such a harsh environment.

Exotic and native trees can be found in all areas of the city. In such a harsh environment, some of the species should not do as well as they are.

In 1948 an Arboretum was established within the parklands adjacent to what is now the City Councils Parks and Gardens Depot, I have been unable to find or locate any records as to what was originally planted within this area, many large established trees are throughout this site. The plantings consist of Australian native species as well as a mixture of exotic species.

Every now and again you will come across something that is different or unusual.

The largest greening program for the city commenced in the early 1970’s, with labour being provided through the Governments RED SCHEMES. Many trees were planted prior to this time by the Commonwealth Railways in their housing estates, by Council and the residents.

At this time there was very little thought given to the mature height of the planted trees, as the majority of the selections were medium to large Eucalypt varieties that were planted to grow through, screen and hide the overhead power lines.

In some areas Eucalyptus camaldulensis seedlings were dug up in the nearby Pichi Richi Pass and Saltia Creek by some of the older residents in the early 1900’s, whilst attending family picnics and replanted within the city especially around some of the ovals and parklands. These trees have now matured and are a valuable tree asset to the city.

The Port Augusta City Council has an annual budget of $88,000.00 for tree trimming and tree removals within the city. Tree planting and general tree watering and establishment is a part of the general Parks sections operational budget.

The parks section aims to plant 1000 trees per year, we find that this number of plantings is manageable for the tree planting and watering team.

Due to our extreme temperatures in summer our tree planting is conducted in early autumn and winter. The trees are watered for the first 3 years, from planting and then in most instances they are left to fend for themselves, unless there are adjacent new plantings the trees may receive supplementary watering.

The city council values its trees, realises and understands what an important asset they are to the city. In the 1800’s, when building first commenced in Port Augusta, the surrounding area was low scrubland and sand hills. The Acacia papyrocarpa,- Western Myall, would have been the dominate tree species in the area.

In times past some of the elected members were only too quick to approve the removal of a street tree, but gladly this trend has changed for the better. A long running debate occurred in council some years ago in relation to the removal of these street trees. The trees remain in place today as the removal motions were defeated.

SAVING THE FORESHORE TREES

Due to the major redevelopment of the foreshore area the original soil surface in this area, had to be raised by a half to ¾ of a meter around these trees to comply with the redevelopment specifications. Instead of removing the significant trees or just raising the soil levels to the desired height around the trees, an actual cement retainer wall/ barrier was poured around the trees. This area adjacent to the tree trunks was then filled with loosely packed stone to allow air movement within the area around the tree trunks.

This then gave us the desired working level and hopefully will not have any major impact on the trees future growth. The stones can easily be removed and replaced if the need arises.

The usual ward system that operates within council has been changed and council has established a Portfolio system, which is where an elected member has been allocated with a goal which is included in the newly endorsed 2004 – 2007, strategic plan.

These sub-goals are allocated to councillors that have an interest, knowledge and understanding in a particular area. The councillors will provide reports on their areas and staff will be required to liaise with councillors in relation to particular topics that they may be working on.

Two of the Goal areas that are part of this portfolio system are Environment Management, and Infrastructure and Resource Management, which street trees are a large part of both of these portfolios.

STREET TREE POLICY, PRACTICES AND PROCEDURES

(the following policy is at this time currently being reviewed, update and re-written.)

STREET TREE POLICY (PRACTICES & PROCEDURES)

Reviewed Council 21/05/02

This policy is directed at establishing firm guidelines for the future development and retention of trees, shrubs, etc. in public streets, reserves and Council owned or controlled areas within the Municipality of the City of Port Augusta.

1. The “Policy” will take into account the following :-

• the local environs and the suitability of trees in those environs;
• the provisions of the Local Government Act 1999;
• the Sewers Act and Waterworks Act (File 1034, 067205), as amended from time to time;
• the Native Vegetation Act 1991 and associated Regulations thereto;
• the Electricity (Principles of Vegetation Clearance) Regulations 1996;

2. Tree planting shall be carried out by, or under the direction of appropriate staff employed by the Corporation of the City of Port Augusta, but must have regard to the “Preferred Tree Planting Species for Port Augusta Environs” (FORG0067).
3. No tree shall be planted by other than Council employees unless prior authorisation has been obtained from the Council. Such permission shall set out any conditions appertaining to the approved planting and shall state :-

• that the tree shall become the property of the Council.
• the resident may care for the tree by undertaking watering, minor pruning and staking etc.

4. Residents shall be encouraged to water their street trees but other care and maintenance shall be carried out by the Parks employees except as outlined above.
5. Trees shall not be planted closer than 10 metres to an intersection where the street width is more than 10.5 metres between the kerbing and no closer than 15 metres where the road paving width is less than 10.5 metres between the kerbings.
6. Trees shall be planted a suitable distance from the kerbing of any roadway thus giving the tree room to develop without lifting kerbing or concrete water tables.
7. Trees shall be planted in footpath areas only when a minimum width from the kerb to the allotment boundary of 3.5 metres exists.
8. The Council will determine what tree species shall be planted in any street or locality.
9. No living tree shall be removed unless authorised in accordance with the provision under delegated authority through Section 44 of the Local Government Act 1999, and evidence of assessment (see FORG0068 “Tree Assessment Form”.)
10. Any new trees or shrubs that are not planted in accordance with this “Policy” will have regard to the “Order Making” Statutory Procedure of the Council (PROA0002).
11. No tree shall be lopped, pruned, removed or disturbed to facilitate the visibility of a sign or advertisement if such tree was in place prior to the erection of any sign or advertisement.
12. In all cases, if there is any conflict between this policy and any Regulations imposed under an Act of Parliament, the appropriate Regulation shall take precedence.

13. Trees that create a health problem for residents and the health problem is identifiable by a medical statement from a Specialist Medical Practitioner, can be removed through a process of written application. All such applications shall be accompanied by details of the Specialist medical opinions and shall initially be considered by any Delegated Employee(s) and be finally resolved by the Council, if necessary.
14. Where trees are deemed as causing danger or hazard to persons and or traffic during non daylight hours, they will need to be removed as expeditiously as possible, taking into account the OHS&W Logging Regulations.

For a “one off” tree removal, (or part thereof), during hours outside normal working hours of relevant staff, this can be done with the assistance of the State Emergency Service (if and where appropriate).

Where more than one tree is to be removed outside of normal working hours, this can be authorised by the appropriate Director or Line Manager and be removed by qualified personnel under the instructions of an appropriate and qualified person, taking into account and abiding by the relevant sections of the OHS&W Logging Regulations.

15. Where there is an application to remove a tree and the Delegated Employee(s) has refused (or intends to refuse the application), the Employee(s) shall organise an on-site meeting with the applicant/resident/owner, together with the Ward Councillor, prior to the application being processed or reviewed.
16. Prior to any street tree removal application being determined (including internal requests) a Tree Assessment Form (FORG0068) must be completed for evidence of assessment and record purposes.

The city council has adopted a selection of preferred tree species that we use as street and plantation trees. These trees have been selected due to their suitability for our conditions, leaf variations and flowers.

Preferred Tree Planting Species for Port Augusta Environs (Group 3)

(REPA2876)

Preferred Tree Planting Species for Port Augusta Environs (Group 2)

Preferred Tree Planting Species for Port Augusta Environs (Group 1)

STREET TREE REMOVALS

The council’s customer services, receives on average 47 phone requests in relation to tree matters in any given month. This is the main area of complaint that is received from the general public, other than rate enquiries and barking dogs!

These requests range from:-

• sucker regrowth from ground stumps
• tree trimming
• collection of leaf litter from footpaths and gutters
• identification of tree species (especially when in flower.)
• visibility hazards
• collection of fallen branches
• dead tree removal
• pedestrian obstructions – low hanging branches.
• Root problems associated with lifting footpaths.

On average Council receives 12 written applications per month requesting street or tree removals.

In many instances the residents do not understand the value and aesthetic value of the trees adjacent to their premises and think that they are a commodity that can be disposed of at any time, with no ill effect on their surroundings, neighbours and street scape if they are removed.

The majority of these requests are in relation to nuisance items including:-

• “The leaves and small branches from the tree drop in my yard and I have to clean my house gutters”
• “nectar and sap from the trees and flowers drops on the footpath and my pavers.”
• The tree smells like cats urine when it is in flower, and I get headaches from it.
• Tree is scraggy looking, I want the same trees as my neighbour
• Killed my lawn which lied beneath them
• The tree could fall on my house at any time
• The tree is shading my new solar hot water panel on the house roof.
• The tree trunks block the view of oncoming traffic, when I try to reverse out of my driveway.
• The tree is very old and it looks as though it has arthritis in the stem! As I have arthritis in my fingers and it looks the same.

These requests are always refused as council will not remove a tree for nuisance value alone.

If a request is received for a tree removal from an elderly pensioner or disabled resident, in relation to leaves in the house gutters, the city council will access the applicant by way of a questionnaire and if the applicant fulfils the stated requirements for assistance, the council will offer a gutter cleaning service through our community services budget line a small fee is applicable for this work and is to be paid for by the applicant. This is conducted through the Men’s Shed program.

The only way that tree removals are approved is if the tree or trees in question are / or

• In a new driveway crossover is to be installed. Usually the proposed driveway is in line with a street tree. Developers give no consideration to the new house placement in regards to street trees.
• pose a safety hazard to the general public, and this hazard cannot be rectified by selective pruning.
• The tree has deteriorated to a stage where its value as a street tree or an infrastructure asset is a hazard to the community.
• If the tree is causing extensive damage to the residents and/or council property and infrastructure and the problem cannot be rectified.

If an application is received for a tree removal in relation to a health issue, eg. Sinus or the tree causes headaches, the application will not be processed unless the resident provides a specialist medical certificate verifying that the applicants condition is attributed to the street tree in question. And not a general medical certificate from their local doctor.

If another section of council wishes to have a tree removed from their area eg. Childcare, nursing home, they also have to apply through the Delegated tree removal process.

ESTABLISHING STREET TREES

In some areas of the city we are experiencing great difficulty in establishing street trees due to ever increasing vandalism and theft. It does not matter if we plant tube stock or advanced trees they are still being damaged or stolen. Usually only the ornamental plantings in the parklands are stolen but we are finding that ever increasing amounts of street trees are also being taken.

The following had been in place for three years, they were advanced trees when originally planted. These trees had reached a height of 3 – 4 meters and one morning it was reported that all the trees within this section of the street had been vandalised. This is disheartening and costly to both the council and the adjacent residents as these residents maintained the trees on behalf of council.

TREENET TRIAL SITE JERVOIS

Our first trial site is situated in the central residential section of Port Augusta. I felt that this was a particularly good site when the resident contacted Council to establish trees adjacent to his newly purchased and renovated premises.

The property is situated at the end of a street and is surrounded by 3 footpath frontages.

As previously mentioned Council does have a selected species listing of preferred trees for footpath planting, which was supplied to the resident for his species selection.

The species requested by the resident was the Golden Leaved Black Locust (Robinia pseudoacacia ‘frisia’) which is not on the preferred street tree planting list, so the only way to establish the trees were by including it as a trial site, which was approved by council.

TREENET TRIAL SITE – ADDISON ROAD

This street situated on the West Side of Port Augusta is 1.2km in length, sealed with kerbing and water table established.

On the eastern side of the street the area is residential housing and on the Western side it is rural living.

At this stage there are very few trees planted within the street and this street has been identified as an ideal site for a trial area, some residents have planted their own trees and these will be included in with the trials. Council will plant more of the same variety so there are approximately 10 – 15 trees of the same variety in the trial. This trial is planned to commence this financial year.

POTENTIAL STREET TREES for trial in Port Augusta

The Port Augusta City Council owns and operates the Australian Arid Lands Botanic Gardens which has various regional plantings of arid land vegetation, even though these plantings are in their infancy stages, many varieties of trees and shrubs that may prove themselves as suitable street tree plantings that are not available commercially, will be sourced from the gardens to be trialled as street plantings.

We conduct plant field collection trips two times per year to the remote outback areas collecting plant material for vegetative propagation and seeds that are suitable for the gardens regional zones.

Our most recent collection trips have been to the AP PITT Lands in the Northern Territory and to Arkaroola in the states far north. On these trips seeds have been collected and these may prove to be suitable varieties for street trees for the arid areas.

Erythrina vespertilio – Bats winged Coral Tree

Deciduous tree to 25 meters in height. Corky bark with small thorns. Red pea flowers to 4 cm appear when the leaves are absent. Bright red seeds in pods 10 cm long.

Grows well in coastal areas as well as inland, frost tender when young and may need protection. Grows in most soils and prefers full sun.

Lyssiphylum gilvum – Bean Tree

Tree to about 6 meters in height, leaves folded like butterfly’s wings, flowers are creamy white. In densely hairy flat – topped clusters. Has a woody seed pod to 7 cm long and flowers in spring.

Maybe deciduous in cooler areas.

This specimen is approximately 24 years of age and is growing in a narrow strip garden bed at the rear of the council offices and is causing no infrastructure damage as yet.

I have noted that the plant will ‘sit’ for a time before showing much upper growth, I put this down to the plant establishing its root system.

Brachychiton rupestre – Bottle Tree

A native of Qld, it prefers medium to heavy soils in an open sunny position, drought and frost resistant and very hardy.

Evergreen or deciduous, it grows to a height of 15 meters with a spread up to 6 meters.

Cream bell shaped flowers occurring in summer.

These trees are 21 years old and are planted in Dempsey Court Port Augusta, West- side.

The footpaths are wide in this street and so far they are accommodating the trees without any problems. It is noted that some of the trees are doing exceptionally well in the street scape. This is attributed to some of the residents watering the trees on a regular basis when they were first planted.

For some reason others are smaller in the street scape. Were they unable to source water from the neighbouring yards?

Bauhinia alba – Orchid tree, Butterfly tree

A native of South America, prefers a rich well drained soil.

Semi deciduous tree to a height of 7 meters with a spread of 4 meters. Large white flowers to 15 cm across.

This specimen is planted in Commercial Road, which is the main street within the city. These trees were planted in July 1984.

The Bauhinias do exceptionally well in Port Augusta and are spectacular when in full flower. These specimens are planted in Commercial Road, which is the main street within the city. These trees were planted in July 1984.

Some of the main problems experienced with the trees are that they require a lot of formative pruning when young as they are fast growing and need to be attended to on a regular basis which may not be acceptable to many councils.

Planted in high profile areas and looked after they are an attraction when in full flower.

Corymbia papuana – Ghost gum

Prefers light sandy soils in an open sunny position and is drought and frost resistant.

An evergreen tree growing to a height of 15 meters with a spread of 5 meters. The stem is erect, smooth and branching, with powdery, white bark, and an open textured spreading crown.

White flowers in summer.

These trees are 21 years of age and are doing extremely well. They have caused no infrastructure damage to the surrounding areas and council has received no complaints from residents in relation to the trees.

Used in America for road side plantings.

Flindersia maculosa – Leopard wood

Beautifully shaped  tree to 12 meters in height with spotted bark. It has a strange juvenile habit of a twisted prickly shrub which eventually sorts itself out into a single stemmed tree, the tree has a pendulous habit when mature. Prefers a well drained sunny position.

Eremophila bignoniflora – Bignonia emu bush

Large rounded shrub up to 4 meters in height, with narrow lanceolate leaves to 18cm in length. The flowers are off white, pendulous and flowering occurs mostly in winter

Melaleuca pauperiflora

A native of WA and SA.

Adaptable to most soils in an open sunny position, and is drought and frost resistant.

Erect almost tree like shrub to 3 meters in height by 1.5 meters in width. The plant has a papery bark with flattened terrate leaves, has white flowers in spring and is a hardy plant in most situations.

Grevillea striata – Beef wood

Medium sized tree to 12 meters in height. Good tree for dry areas.  Mature tree has rough dark bark, leathery linear leaves to 45 cm in length. Cream flowers in spikes to 8 cm in length. Prefers a well drained sunny position.

Eucalyptus populnea – Bimble box

Evergreen tree growing to a height of 25 meters. Native to SE Qld and NE Nsw, prefers heavy, clayey soils in an open sunny position, drought and frost tender.

Light greyish brown fibrous bark and a densely textured crown. Flowers are white and occur in late summer.

Koelreuteria bipinnata – Golden rain tree

The Koelreuteria is a deciduous tree that has a rounded canopy. It is a medium sized rapid growing tree.

The flowers are yellow and the papery seed pods are salmon- pink in colour.

It is  drought tolerant and can tolerate poor drainage, poor soils and temperature extremes.

The deep non- invasive root system rarely disturbs side walks. ( have to wait and see!!)

This species of tree does exceptionally well within the city. Withstanding all weather conditions. It is a handsome tree that is becoming popular with residents that wish to have a deciduous tree adjacent to their premises. Some residents have requested plane trees as their preferred plantings but have been content to have the Koelreuteria species as a substitute.

The trees germinate readily from seed and may become a problem to the residents with seedlings in their yards.

The Koelreuteria paniculata does not perform well in the city, having the larger leaf surface the trees always look dry and burnt from the winds that are experienced here.

Fraxinus griffithii – semi- evergreen ash

This is a small to medium height semi evergreen tree that is becoming popular with some of the residents of Port Augusta as a street tree. This is due to the local garden centre ‘pushing’ the tree as a street tree to its customers. I have noted that some plants do better than others in the same area, whether this is due to the soil conditions and nutrient availability or to the genetic make up of the trees themselves I do not know. I have not been able to find a mature specimen in the city to compare the plantings with.

Hibiscus tiliaceus

Evergreen tall tree up to 20 meters in height, deep sunken tap root. Bark greyish black. Yellow flowers in the shape of a single hibiscus, 4 cm long by 5cm wide, very showy when in full flower. Plant is easy to strike from cuttings.

Kigelia pinnata – South African Sausage Tree

This specimen is growing on the edge of Apex Park in Port Augusta. The tree is approximately 40 years of age it tolerates the extreme summer temperatures that are experienced in the city. There has been no damage caused to the surrounding cement garden borders or damage to the adjacent sealed footpath area.

The tree flowers from August to November with fragrant, bell shaped, deep maroon or claret, green or yellow veined flowers, they form on hanging, 15 – 30cm flower stalks which open one at a time.

The mature fruit maybe a problem.

WHAT WE HAVE FOUND NOT TO PLANT

The following trees listed are species that we have found to cause the council problems and in some cases extensive problems and are unsuitable in our area as a street tree, do not get me wrong, as I am not recommending that these trees should not be planted or trialled, as they maybe suitable in other areas as street tree specimens.

An example of this occurred when David and Sean visited last year. We were driving along and I was explaining to David the problems that we have with Eucalyptus erythrocory’s in the streets and that we do not plant them anymore, and David felt that these were some of the best specimens that he had seen!

Phytolacca dioica – Ombu tree

This is the only known remaining tree of this type in the city. This tree has been planted on a footpath in Paringa Road. The tree is encroaching into the driveway of the adjoining residence and Council has never received a complaint from the resident in relation to the tree. The resident removes the basal epicormic growth each year and disposes of the material.

Casuarina and allocasuarina species- Black oak, swamp oak

During the early planting within the city in the 1970’s many Casuarinas were planted.

At the time they seemed like ideal trees for the street, nice erect shaped trees that were easy to prune to a desired pedestrian height, not a lot of leaf litter no problems with bees, but now we are experiencing problems with suckers from some varieties.

The suckers grow in the resident’s yards, along the footpaths, kerb line water table and we have even had them grow in the centre of the sealed roads where the bitumen had cracked.

Problems are also experienced with the roots in storm water drains and sewer pipes.

Shinus mollee – pepper tree

The pepper tree does exceptionally well in our arid areas, they are a beautiful large tree. Council does not allow the planting of these trees within the city due to the associated root problems that are experienced with infrastructure and private residences. The existing trees in road reserves and parklands have been left but the majority of street plantings have been removed.

Acacia salicina – Broughton willow

This variety of tree also causes extensive problems with their suckering root systems with both council’s infrastructure and also with residents. A lot of complaints are received by residents in relation to the flower and pollen problems with this particular species. These trees are an ideal smaller specimen, particularly suited to salty areas and reserves where the suckers can be allowed to grow.

Acacia saligna – Golden Wreath Wattle

Very fast growing and showy tree when in flower, but is prone to blowing over.

Also it is one of the shorter lived acacias. Problems are experienced with extensive root suckering as the tree gets older and as it begins to deteriorate.

Ceratonia siliqua – Carob tree

Ideal for larger park areas, but not that suited to the footpaths. The extensive size of the trunk and roots cause problems with kerb lines and water tables, not the best under powerlines either.

The tree will tolerate extensive crown reduction and recovers well.

Santalum acuminatum – wild peach

This would be suitable as a street tree planting if the branches were not so brittle. We have found that with existing trees when they are fruiting the trees are stripped of branches by pedestrians gathering the fruit.

In a couple of instances the trees had to be removed due to suckering, on one corner alone there were two trees and 75 smaller suckering growths in the surrounding footpath area.

Eucalyptus erythrocory’s – Red Capped Gum

Problems are experienced with this tree in all areas of the city. It is very hard to get a straight tree due to the windy conditions in the city. Most of the trees of this variety are on a lean, the large fruiting capsules cause branch drop due to their weight, the nectar from the flowers will even discolour the paint on your car when you try to remove it.

When the stump is ground out and removed, the tree will often send up sucker regrowth.