They have resorted to erecting signs stating the type of the tree, its individual cost and the cumulative cost to ratepayers of repeatedly replacing the trees.
They are designed to raise public awareness of the ongoing vandalism issue.
Foreshore team leader Jamie Davies said they had put up 25 signs so far, mostly along the foreshores of Applecross, Attadale and Bicton – the hotspots for the offending.
“We’re at a loss as to why young trees keep being vandalised considering there is little chance that they will interrupt views, they complement existing mature native trees on the foreshore and don’t create any other foreseeable inconvenience,” he said.
“There are already well-established trees on the foreshore, and we get no complaints about those.”
City of Melville chief executive Gail Bowman estimated each tree costs about $450, including the cost of the tree and its upkeep including labour and maintenance.
“Keep in mind some the trees have been nurtured from tube stock and may have been growing years before they reach sapling stage and are then vandalised,” she said.
“The vandalism of trees costs the City and ultimately ratepayers considerable money as well as going against the urgent need to address climate change.
“I encourage anyone who witnesses vandalism to trees in our parks, bushlands, wetlands or river foreshore reserves to report it to the City.”