Police are investigating the deliberate poisoning of six mature pōhutukawa trees on public land on the Kāpiti Coast.
District council parks manager Alison Law said staff doing routine maintenance in McLean Park at Paraparaumu Beach last week noticed the trees were dying, and found a granular substance sprinkled around their roots.
She said tests have confirmed it was a high-grade herbicide called Picloram.
"We don't use that herbicide in our parks so because of that we're presuming that someone has done it to purposefully harm the tree."
She said the trees cannot be saved and would need to be removed.
And she said unfortunately the poison has contaminated the ground, and the site cannot be replanted for at least a year.