Issues for Tree Management in the Public Arena
A Case Study of Hyde Park Tree Management

K. Sweeney

INTRODUCTION

Hyde Park is one of Sydney’s premier parks and has an area of 16.7 hectares of land in the CBD of Sydney. Hyde Park attracts over 2 million visitors per year with its main features including the Archibald Fountain, Pool of Reflection, Anzac Memorial and the avenue of Hills Figs through its centre.

On the 8 October 2004, the City of Sydney Council undertook the urgent removal of seven (7) Ficus microcarpa var. Hilli (Hills Fig) from Hyde Park’s main avenue planting.

This paper examines tree management issues within the public arena and the process required to remove significant trees once they have become dangerous.

HYDE PARK - A BRIEF HISTORY

Hyde Park is Australia's oldest park and was gazetted in 1810. Hyde Park is classified as Crown Land and has been managed by City of Sydney Council since 1904.

The original avenue planting of Ficus macrophylla (Morton Bay Fig) planted in 1862 was removed to allow for construction of the City Circle underground railway, built from 1918 – 1926, and reportedly sparked a public outcry.

The main avenue of Ficus microcarpa var. Hilli (Hills Figs) was planted in the 1930’s, linking the Archibald Fountain in Hyde Park North with the Anzac Memorial in Hyde Park South. The avenue now consists of 148 Hills Figs, from Hyde Park North to South, that are in varying stages of health and condition.

ISSUES ARISING

The key tree management issues facing Hyde Park, which can also be applied to many of Sydney’s other 19th Century Parks, include:
• Tree failures
• Significant disease issues
• Ageing tree population
• Avenue plantings and their inherent issues
• High visitation rates/Sense of ownership
• Cultural usage and events
• Public consultation and education
• Political arena

Previous Tree Failures
In the past 4 years, one (1) Hills Fig in Hyde Park North and three (3) Hills Figs in Hyde Park South have failed from the main avenue. Three (3) of the trees failed within an 18 month period, with the most recent failure occurring in July 2004.

This failure resulted in the 20 metre tall tree landing on the main avenue pathway at approximately 9am on a Sunday morning. Fortunately there were no injuries to people or major property damage sustained.

The cause of tree failure was due to advanced decay of the structural roots (by the white rot fungi Phellinus species) in conjunction with strong winds. Further investigations were then undertaken on selected Fig’s, which exhibited signs of decline or disease such as fungal fruiting bodies, to determine the extent of decay.

The investigations revealed the trees were affected by three (3) diseases, Phytophthora, Armillaria and Phellinus. Seven (7) trees were considered imminently dangerous and required urgent removal.

Impact of Disease
There are three (3) diseases that are affecting the Hills Fig’s health and structural stability.

Phellinus species
Phellinus is a genus of white rot fungus. These fungi generally degrade the lignin (strengthening material) components of the wood more rapidly that the cellulose (sugars) and lead to reduced wood strength. The decayed areas within the tree may extend 2-3 metres above or below the fruiting bodies.

Phellinus is thought to spread via spores off the fruiting body, found at the base of the tree trunk and through root to root contact in the soil.

The habit of the fungi and the methods of control are not known at this stage.

Armillaria luteobubalina
Armillaria is a soil borne fungus that causes root rot in a variety of native and exotic plants. The symptoms of the fungus include the death of branches, yellowing of foliage, poor vigour and the darkening and rotting of the larger roots.

During May to June, small mushrooms under the trees canopy or on the trunk and white threads of or fungi growth under bark trunk indicate a tree is infected with the fungus.

Armillaria spreads through root to root contact with infected trees, especially old decayed stumps and roots.

At present there is no simple method for controlling Armillaria so combinations of treatments are required. This includes the complete removal of the infected tree, including the tree stump and roots where possible and delaying the planting of new trees for as long as possible.

Phytophthora cinnamomi
Phytophthora is a microscopic soil borne disease that causes root rot in a wide variety of native and exotic plants. The pathogen is a virulent species and is of great concern as there is no known control.

Infection often results in the death of the plant, with earlier symptoms including wilting, yellowing and retention of dried foliage and darkening of young feeder roots and occasionally the larger roots.

The pathogen spreads through small swimming ‘zoospores’ and attach and infect roots. The spores and structures of Phytophthora are microscopic and cannot be seen with the naked eye. There is no way of visually telling if the pathogen is present in the soil.

These spores are easily transported in storm water, drainage water, contaminated soil and on tools, footwear and vehicles. The spores are also capable of surviving for extended periods of time, and when conditions become favourable they germinate and renew the life cycle. This allows Phytophthora to survive in dead plant tissue for a number of years.

At present there is no one simple method for controlling Phytophthora cinnamomi. A combination of sanitation measures, good horticultural management, and selective use of some fungicides and the addition of organic matter to soils can be used to retard the activity of Phytophthora.

TREE REMOVAL PROCESS

The removal of significant trees in Sydney is a very sensitive and often controversial issue, as recently highlighted by the Cahill Expressway and Domain Fig tree removal. Due to the sensitivities surrounding significant tree removal, the process required to remove the 7 Hills’ Figs was involved and is briefly detailed below:

• 2 Independent Arborist Reports commissioned
  The reports were accessible form the City’s website following the City’s press release and media statements.

• Approval from the City’s General Manager to remove the seven (7) Hills Figs

• Lord Mayor and Councillors briefed
  This incudes a site inspection with interested parties explaining the management issues. The trees thinned canopy coverage and fruiting bodies was highlighted.

• Timing of Removal
  The City’s main event in Hyde Park, Art & About, was programmed to commence within 3 days time. This event invites more than 500,000 people to come and view large scale art from underneath the trees in the main avenue.

• Exclusions zones created
  Safety barricade fencing erected around each of the seven (7) trees to stop pedestrian access within the trees fall zone. Fencing blocked the main avenue adjacent to the Archibald Fountain. Security guards engaged to keep any public or protestors out of safety zones.

• Community Notification and Media
  Press releases and media statements issued to all newspapers, television and radio stations. Storey boards and Fact Sheets erected on barricade fencing around the Park. City’s website continually updated with information.

• Site Contingencies
  Contingencies for the site were made in the event of protestors or adverse weather conditions.

All seven (7) trees were removed on the Friday without incident and the site was reinstated for the opening of the Art and About Exhibition for the Saturday morning.

One tree stump was retained on the site to allow the community to view the extent of decay at the trees base. Signage was erected to explain the decay and its impact upon the trees structural stability. This stump was removed following the completion of Art and About.

TREE MANAGEMENT PLAN

The City is currently developing a Tree Management Plan for Hyde Park and will form a major part of the Hyde Park Plan of Management.

The Tree Management Plan identifies the long term vision for the parks trees and details the strategies for implementation. The key areas of the Management Plan include:

• identification of the special qualities of the existing tree population and the landscape character that they create;

• provide strategies for the long term removal/replacement of all of the park’s trees, setting priorities for Hyde Park North and Hyde Park South;

• to develop a consistent proactive management approach for the existing tree population, in particular the avenue plantings;

• assess the health and condition of all existing trees;

• develop a clear planting philosophy; and

• develop community awareness and acceptance of tree removal and replacement practices.

The Hyde Park Tree Management Plan will give the community and Council a clear direction and vision for the future management of the park’s significant trees.

ACKNOWLEDGMENTS
I would like to acknowledge and thank Mr Peter Castor for the information provided on the tree failures and Dr Brett Summerell for the information on the diseases and their habit and control.

back to top