Gunning for gunnera

Managing the prolific weed Gunnera tinctoria

Part I

Background

Otago Regional Council (ORC) recently GPS-mapped sites along Bullock Creek in Wānaka, identifying eighteen sites where gunnera (Gunnera tinctoria) was found alongside the creek and its tributaries. From these eighteen sites, with funding generously provided by Central Lakes Trust and Wānaka Rotary, Paul and Ed from FOBC have begun gunnera removal, with additional sited identified as needing gunnera removal numbering at least forty.

The removal work began around mid-February and is in conjunction with private landowners who have given permission to access the tributaries running through their land where gunnera is growing. Paul is door-knocking houses based on the eighteen original sites identified by ORC. It is critical to have landowner cooperation with this project, to allow access to first identify and then remove the gunnera from alongside Bullock Creek. One landowner described how they’re happy to be involved because it means the health of the waterways is being looked after.

What is gunnera and why is it a problem?

Gunnera, also known as Chilean rhubarb, is a large growing clump-forming plant, classified as a National Pest Plant Accord (NPPA) plant and a DOC-identified environmental weed[1] in Aotearoa New Zealand.

The plants can grow so big, with some of the larger leaves measuring at least a metre wide or more, which is massive! The shade they create negates ideal light and growing conditions for other plants, essentially out-competing other plants for light and space; Ed says that only some shade-loving species can survive in the midst of gunnera. Because gunnera easily spreads and grows more seedlings through its root system and even from stalk cuttings, it poses a huge competition risk to native plant species that would otherwise grow in similar conditions.

Look how big just one stalk and leaf is compared to Paul!

 “They can take over hectares”, according to Paul, who goes on to explain that “the spores release when its mature”, creating ample opportunity for gunnera to spread.

How does gunnera spread?

Spores from mature plants are dispersed through the waterways, hence why so many are found along Bullock Creek and its tributaries, as well as being spread by birds[2]. The plant is often found in high-rainfall and wet areas, and has even been spotted on West Coast beaches.

Big heavy flower heads full of seeds.

What is involved in gunnera management?

A lot of hard work! It is a physical job removing gunnera, and Paul and Ed have been hard at work attending the eighteen identified sites and the additional sites where gunnera is known to be growing along Bullock Creek and its tributaries. Stay tuned for the next instalment to find out more about the removal and management work as well as ways you can be involved in this waterway health initiative.

References

[1] New Zealand Plant Conservation Network 2025 and Otago Regional Council 2025

[2] Environment Southland Regional Council n.d.