A 2012 survey identified 113 different weed species in Abel Tasman – not including gorse and hakea.  Many of these are common garden plants that have jumped the fence and found the national park more to their liking, which is why local bach owners play a key role in weed control.
The park’s 113 weeds species are mostly associated with former farms and bach areas. They have the potential to seriously compromise native forest regeneration if not brought under control.

In 2014, the Abel Tasman Birdsong Trust began a $200,000 weed control programme, supported by the New Zealand Lottery Grants Board, targeting high-priority weeds like grevillea, wattle, holly, old man’s beard, pampas and tradescantia.  At Totaranui, climbing vines like Japanese honeysuckle, jasmine and banana passionfruit, and willows in the wetland area were controlled.

Project Janszoon took over follow-up work in 2016, focusing on target species that were either missed, or had sprung up after initial control.  DOC continues to manage boxthorn and the aggressive Australian wonga wonga vine in the north of the Park.

Bach owners have been very supportive, removing plants on private land that were causing problems in the Park. Old man’s beard and banana passionfruit on the Park’s western fringes are also sources of reinvasion, so Project Janszoon has collaborated with Project De-Vine in this area.

Looking forward, as the existing weed problem is reined in, the test will be to prevent the introduction of new weed problems into the Park – a challenge that will require Project Janszoon, landowners, DOC and the Tasman District Council to work together.

Photo credit Wade Million, Project DeVine

The Filthy 14

While there have been 113 different weed species identified in the Abel Tasman National Park, Project Janszoon and the Abel Tasman Birdsong Trust are particularly interested in what we call the “filthy fourteen”.

Each of these plants poses a threat to the park in different ways. If you see or suspect any of these species in or around the park, please let us know. You can email sightings to info@janszoon.org or via the ‘Have you seen this?’ section of the Abel Tasman Phone App.

A plan to help Black Beech control hakea

A trial to grow black beech in areas with low-fertility soils may be the answer to controlling the exotic weed hakea in these areas. But it will take many years to see results.

Two species of the invasive weed Hakea are well established in the Park. As early colonisers they make their presence known particularly on infertile or denuded sites. They can be easily be seen on Adele Island and on the ridges behind Anchorage. Hakea is not easily controlled by cutting or spraying due to its prolific seeding.

In 2014 DOC and Project Janszoon began the black beech planting trial on Motuareronui Adele Island looking at beech tree survival in areas of harsh, low-fertility soils that have been burned in the past. Volunteers from Motueka High School and the Abel Tasman Birdsong Trust have helped plant and monitor the beech which are grown with mycorrhizae fungi, which associate with the roots and help the tree draw nutrients from the soil.
Three years later, the trees have had a 93% survival rate which has given researchers the confidence to take the trial to the mainland. Sites are being scoped near Anchorage for planting in 2018 when more trees will be available locally.

Ultimately, it is hoped beech tree forests will reestablish on lowland ridges and headlands where the trees would once have dominated. In turn this will help to restrict the spread and growth of hakea, which prefers a lot of light to survive.