Sydney council erects banner after century-old tree poisoned on leafy north shore

Hornsby council is investigating the suspected poisoning of a turpentine tree, thought to be around 100 years old, in Thornleigh, on Sydney's upper north shore.

The council has tied a banner to the tree on Goodlands Avenue, which states, "This tree has been poisoned", and urges anyone with information about what happened to the tree to come forward.

The turpentine tree is one of the dominant species of the critically endangered Sydney Turpentine-Ironbark Forest, which has only 0.5 percent of its original distribution remaining.

The unique ecological community is present in several suburbs within the Hornsby shire, including Thornleigh, and is protected under both NSW and Commonwealth legislation.  

A spokesperson for Hornsby Council said the tree had been assessed by two council aborists who found eight drill holes in the trunk.

"Assessment of the upper canopy indicates that the tree was poisoned by the dead leaves that are retained on the branches," the spokesperson said.

The tree was unlikely to survive, they added.

"Most of the canopy is dead, and it is unlikely the tree will recover," the spokesperson said.

The tree's suspected poisoning was reported the council in March and aerial photography from January 2025 showed the tree in good health.

It is unknown exactly how old the tree is, however, one knowledgeable local estimated the tree was about 100 years old. 

"The tree can be seen as a large specimen in 1943 aerial photography, so it is more than 80 years old," the council spokesperson said. 

Turpentine trees typically live to about 300 years old.

The tree poisoning is not an isolated incident, with the council investigating other recent indications of tree poisoning in the area, as well as across the Hornsby shire.

"As the Bushland Shire, maintaining and reinforcing our tree canopy is a high priority for Council," Hornsby mayor Warren Waddell said. 

"Our staff are investigating the circumstances behind this suspected poisoning."

Some Sydney councils have gone to extreme lengths to stop suspected tree poisonings.

Last year, Lane Cove Council erected a huge banner which blocked prized views of Sydney Harbour in Longueville last September after almost 300 trees were illegally killed.

Residents in Castle Cove, on Sydney's north shore, were shocked in August when 265 trees were decimated by a person or gang wielding a chainsaw and poison. A $10,000 reward was offered to track down those responsible.

In March, nine historic fig trees were poisoned at Sydney's Balmoral Beach, shocking locals, however, in that case, the trees survived the attack.