Under the Lens: Weeds Hidden in Plain Sight

5 December 2025

Episode 5: What is green blindness really hiding?

We explore the growing weed problem across Aotearoa New Zealand. Professor Margaret Stanley joins us to explain how weeds spread, why new species keep emerging, and what tools we have to manage them. From garden escapes to biocontrol success stories, we look at the practical steps communities and councils can take to protect our landscapes and stop the next wave of invasive plants.

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Episode Highlights

What counts as a weed and why definitions matter for management
Plant blindness and why “just green” can hide serious invasion
How many introduced plants we have in Aotearoa and how many have become invasive
Pathways for new weeds including gardens, horticulture, forestry, illegal imports, machinery and garden waste dumping
Emerging weeds and why around 20 new species establish in the wild each year
Strengths and limits of herbicides, manual control and biocontrol
Biocontrol stories such as St John’s wort, mist flower and heather
Climate change and the southward and uphill spread of subtropical weeds
Aquatic weeds, hydrodams and the difficulty of underwater control
Native versus exotic plantings in our cities and how this shapes biodiversity and cultural connection
The critical role of community surveillance, reporting and volunteering

Episode Description

Weeds are everywhere in Aotearoa New Zealand. They creep along roadsides, smother forest edges, clog waterways and hydrodams, and quietly take over harbour hillsides. Most of us just see green.

In this conversation, Professor Margaret Stanley, recently recognised as Science Communicator of the Year, helps us see what is really going on in that green backdrop. She explains what makes a plant a weed, why only a small fraction of introduced species become invasive, and how new weeds continue to “jump the fence” from gardens, forestry, horticulture and houseplants.

We look at problem species like banana passionfruit, ragwort, agapanthus, climbing asparagus, aquatic weeds and more. Margaret talks through the tools we currently have, from herbicides and hand-pulling to biocontrol agents like beetles and rust fungi, and why each tool has limits.

The episode also explores how climate change will shift weed ranges, why aquatic weeds are so hard to manage, and how nursery choices, urban planting and cultural values shape the plants around us. Above all, it highlights the role of communities in early detection and prevention through tools like iNaturalist, local council programmes and on-the-ground volunteer mahi.

Meet our Guest

Professor Margaret Stanley

Professor Margaret Stanley is an ecologist at the University of Auckland with expertise in biodiversity, biosecurity, conservation, invasive species and urban ecology. Margaret’s research focuses on understanding and reducing the impacts of people on terrestrial biodiversity, particularly in relation to invasive species and urban development. She works with a wide range of research partners, biodiversity and biosecurity agencies and community stakeholders to ensure her research supports effective decision making.

Margaret is a researcher with Bioprotection Aotearoa, contributing to the weeds research programme and supervising postgraduate students as they progress their PhD projects.

She is also a passionate science communicator and recently received the 2025 Callaghan Medal for her outstanding contribution to science communication and for raising public awareness of the value of science.

Meet the Hosts

Professor Amanda Black — Director, Bioprotection Aotearoa; soil scientist at Lincoln University.
Professor Peter Dearden — Co-Director, Genomics Aotearoa; geneticist at the University of Otago.
Dr Nick Waipara — Forest pathologist with Plant & Food Research Group of the Bioeconomy Science Institute, and a long-time collaborator with Te Tira Whakamātaki.

Glossary of Key Terms

Invasive weed
A non native plant that spreads aggressively and causes ecological, economic or cultural harm.

Plant blindness
When people see vegetation as a uniform green background and struggle to notice or identify individual plant species, including weeds.

Propagule pressure
The idea that the more a plant is planted or moved around, the higher the chance it will establish and spread in the wild.

Biocontrol (biological control)
Using living organisms such as insects, mites or fungi to reduce the population or impact of a weed.

Emerging weed
A plant that has recently begun to establish in the wild and has the potential to become invasive if not detected and controlled early.

HSNO Act
The Hazardous Substances and New Organisms Act, which tightly controls new organisms entering Aotearoa.

Check, Clean, Dry
A prevention campaign that asks people to clean boats, trailers, fishing gear and other equipment between waterways to stop aquatic pests and weeds spreading.

Fleshy fruited plant
A plant with soft fruit that is attractive to birds. Seeds are often spread over long distances in bird droppings.

About the Podcast

Under the Lens is a conversation series exploring how ecosystems resist, recover, and thrive across Aotearoa New Zealand and the Pacific.

Our Voice

Warm. Curious. Grounded.

We welcome tough questions, speak in plain language, and focus on real people and real impacts. Our conversations bridge perspectives and explore how knowledge, experience, and action come together to support resilience across Aotearoa.

Where This Episode Fits

This kōrero bridges our early discussions about ecological pressure with the emerging technologies that might help us respond. By exploring genetic modification, gene editing and the history behind Aotearoa New Zealand’s GM debates, we build the foundation needed to understand the practical challenges ahead.

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