Opinion: Curse of the Christmas tree

Opinion: Curse of the Christmas tree

It’s arguably the biggest pest in New Zealand, but one of the least known.

Pinus contorta, otherwise known as wilding pine, may look like a lovely Christmas tree, but it is a vicious weed which is strangling the life out of our forests.

It has already infested seven percent of the country – 1.7 million hectares.

Left unchecked, it’ll infest 20 percent of New Zealand within two decades.

Not to be confused with pinus radiate, the common tree in forestry blocks, pinus contorta is a nasty, twisting tree, and it is rampant.

This is not just a conservation issue; the cost to our economy is estimated at around $1.2 billion.

Wilding pines quickly smother forest – native and introduced. That’s bad news for forestry, beekeepers, tourism operators, hunters and farmers.

These fast-growing trees suck up enormous amounts of water. Clearing the land of wilding pines increases water yield by about a third.

In dry areas like the Mackenzie Basin or Hawkes Bay, that’s water that could potentially be used for irrigation. Instead, it’s being used by wilding pines to continue their spread.

The Department of Conservation (DOC) is trying to control the pest, but it’s tough, particularly with the crippling budgetary constraints placed upon the department.

A single pinus contorta can produce 17,000 seeds – and its lightweight pinecones can float for up to 20km. Within three years, the young trees that grow from those seeds will produce pinecones of their own.

It’s a difficult tree to kill. Not only do you have to saw the trunk at pretty much ground level, you then need to also clear any tiny green shoots left around the stem. If you fail to do this it’ll grow back like some real life hydra, more twisted and gnarled than before.

The time to get them is when they are young. Removing small trees costs $10 per hectare. Removing mature wilding pines costs $10,000 per hectare.

You can poison them form the air, but helicopters are expensive. You can kill them on the ground, but stem-drilling and herbicide injections take time.

This is not just DOC’s problem. Regional councils, community groups, businesses – they all have a part to play. One plot I was shown had been cleared of contorta thanks to sponsorship from Arataki Honey, because if wilding pines smother the manuka forests where their bees forage, their valuable business will suffer.

This pest can be stopped, and it is going to take a huge effort.

But whatever the cost, whatever the resource, we need to do it. We simply can’t afford to do nothing.

There is large and growing support in the community as demonstrated by the number of wilding control groups.

NZ Wilding Conifer Management Group

The Wakatipu Wilding Conifer Control Group

Waimakariri Ecological and Landscape Restoration Alliance

Marlborough Sounds Restoration Trust

 Ohau Conservation Trust


Wanganui Tramping Club

Regional Councils, Forest and Bird, and DOC also run volunteer days.