The Queenstown Lakes District Council is pleading for people to stop vandalising trees in the town.
The council said a number of birch trees along Marine Parade, planted as a memorial to fallen World War One soldiers, were deliberately vandalised last week.
Two trees had suffered cuts in the bark by a large knife or small axe, while another had a sad face "crudely" carved into the bark.
Several recently planted Lombardy poplar trees in St Omar Park are also being illegally pruned on a regular basis.
The council's arboriculture officer, Tim Errington, said any damage could seriously harm trees, and people should treat them with respect.
"Anything that penetrates through the bark layer to the wood below has the potential to stunt or even kill these trees...this severs the vessels that transport sugars produced by the leaves to the rest of the tree, and by disrupting this crucial transport system it reduces the trees' vigour and vitality," he said.
"In addition, these open wounds are now an entry point for organisms such as decay fungi, viruses and wood digesting insects to get into the trees, potentially causing further harm."
Mr Errington said if people wanted to carve a face or initials into a piece of wood they should use something that was not alive.
"A number of the trees in our region are much older than anyone alive in the district today, and it would be an absolute tragedy to lose them because of an irresponsible act," he said.
"For those who see fit to take it upon themselves to prune and dismember community-owned trees, please just get in touch with us to see if we can come to a solution before taking the matter into your own hands."