Managing the prolific weed Gunnera tinctoria

Part II

Big, big, big gunnera leaves

The removal and management work

A ‘cut and paste’ method is being used to manage and remove the gunnera found along Bullock Creek and its tributaries. Firstly, the plant stalks are cut down with shears and saw; some of the stalks are more than 15cm in diameter and can weigh at least 7kg or more, depending on how big the leaves are. Secondly, after the stalks have been cut as close to the ground as possible, a herbicide paste is applied directly to the exposed stem, which works to completely kill the plants, spreading through the remaining vascular system. Given that the application of herbicide is being done in the close vicinity of the creek and nearby to other non-target plants, Paul and Ed are very careful to ensure the targeted and judicious use of the herbicide to the gunnera being cut down.

Ed pasting the stumps

This combination of physical and chemical management of gunnera helps to firstly manage existing stands of the plant, whilst also reducing their ability to spread and grow elsewhere. While the cutting and pasting method is effective, it is important to note that even once the plants have been cut down and poisoned, the remaining stumps and root systems can still impact the immediate vicinity and the ability of other plants to repopulate that area. Therefore, it is of critical importance to identify and manage gunnera when it is a smaller plant, to avoid the potential larger-scale problems they can cause as they grow into mature, and very large, plants.

Cutting the last one…a big job

 After being cut down, the stalks and leaves of gunnera are taken to the green waste disposal site where they are then mulched and process to become compost or topsoil. A nice closed loop from foe to friend in the garden.

A trailerful of gunnera, bursting at the seams

What can I do to help?

If you’re a landowner or have responsibility for any creek-side land, you can do your bit by removing gunnera where and when you see it. You can also contact us for more information or for help in the process. For more information about managing gunnera check out this page from ORC: https://www.orc.govt.nz/environment/biosecurity-and-pests/plant-pests/gunnera/

If you love the wetlands and waterways regeneration work we do, you may want to volunteer with us or you may want to make a donation to help continue our work. Check out our website for more information www.fobc.kiwi

With thanks to Paul and Ed, Central Lakes Trust and Wānaka Rotary, and cooperation from local landowners enabling the important weed removal work in the name of ecosystem and waterway health.

References

Environment Southland Regional Council. (n.d.). Chilean rhubarb. https://pesthub.es.govt.nz/?pwsystem=true&pwid=543&sort=alpha

New Zealand Plant Conservation Network. (2025). Gunnera tinctoria.

https://www.nzpcn.org.nz/flora/species/gunnera-tinctoria/

Otago Regional Council. (2025). Gunnera. https://www.orc.govt.nz/environment/biosecurity-and-pests/plant-pests/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.