Trees have been poisoned in the Bay of Islands with a Paihia couple discovering several specimens dead or dying on their property.

Lisa Harris and Daniel Gonin returned to their Sullivans Rd home in January after a nine-month stay in Australia to find several trees on and around their property were dead or sickly.

A large banksia on council land at the corner of their driveway had died completely but it was only when an arborist found a series of small holes at the base of its trunk that they realised it had been poisoned.

That was confirmed last week by a Far North District Council staff member.

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The discovery spurred the couple to examine other ailing trees on their property, which revealed others too had been drilled.

Daniel Gonin points out the hole in an ailing banksia tree. Photo / Peter de Graaf
Daniel Gonin points out the hole in an ailing banksia tree. Photo / Peter de Graaf

The death toll includes the banksia and a large mānuka. A second banksia appears to be dying along with the tallest tree on the property, while a number of smaller mānuka have been cut down.

Harris said the couple had planted the banksias 25 years ago, five years after moving to Sullivans Rd from Switzerland.

At that time their house was one of only two in the immediate area; now they are surrounded by top-end homes, many of the built in the past few years.

''I am maybe silly, it is romantic, but the trees are our babies, we pamper them. They take 20 years to grow, the birds come and they give us oxygen,'' Harris said.

They planned to leave the dead trees standing.

''We could cut them down and plant new ones but then they have won, they will have the view.''

One of a series of holes drilled in an ailing banksia tree. Photo / Peter de Graaf
One of a series of holes drilled in an ailing banksia tree. Photo / Peter de Graaf

Gonin said the ground in the area was unstable clay.

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''Without the trees, it [the soil] will be gone. They take a long time to grow. It's a crime,'' he said.

The poisonings and the resulting suspicions have sparked something of a feud in the neighbourhood with residents, including the Swiss couple, issuing trespass notices against each other.

It's not new either. In 2005 a 20m-tall totara in their backyard was poisoned and had to be cut down.

A council spokesman said a staff member had investigated a complaint lodged on February 22 that trees had been poisoned on Sullivans Rd.

The trees, which were on both private and council land, were found to have drill holes. Some were already dead.

An arborist was due to inspect the trees this week due to concerns that one could damage a house if it fell.

The poisoning has also been reported to Mid North police.

Meanwhile, an investigation into the poisoning of four beachfront pohutukawa at Opito Bay, near Kerikeri, is continuing.

In November local residents discovered the ailing trees' roots were riddled with drill holes. The council called in police in December after being unable to identify the culprit.

An arborist is checking the trees monthly and removing branches as they die.