Common name: Chilean rhubarb or Giant rhubarb
Botanical name: Gunnera tinctoria
Management programme: Advisory
Originates from Chile and Argentina. Introduced to New Zealand as an ornamental garden plant and naturalised in 1968. It looks similar to rhubarb but is unrelated. Gunnera species are known for their symbiotic relationships with cyanobacteria. The blue-green algae Nostoc is found in the root nodes where it fixes nitrogen into the soil.
Why is it a pest?
- Chilean rhubarb forms dense colonies with large leaves shading out and suppressing native vegetation.
- It can eventually dominate stream and lake margins.
- It produces an abundance of viable seed, approximately 250,000 seeds in a year. Seeds are spread by water and birds, and remain viable for 2-3 years.
Where is it found?
- Is generally found in gardens and along swampy areas, roadsides, lake edges and streams.
- Chilean rhubarb can also spread vegetatively by growth of rhizomes and regrowth from rhizome fragments.
- It is found scattered throughout New Zealand but mostly in areas of high rainfall such as Taranaki, where over 40km of coastline is badly infested.
- Has been noted throughout the Bay of Plenty.
What does it look like?
- A giant rhubarb-like herb up to 2m.
- Massive, rough, and wrinkled umbrella sized leaves (80cm x 1m) on sturdy stalks up to 2.5m tall and have 5–7 lobes with raised veins beneath.
- Both leaves and leaf stalks are covered in rubbery red prickles.
- The inflorescence is a spike of 50-75cm, up to 10cm in diameter, bearing very small flowers.
- Flowers October/November.
What are the rules?
The Bay of Plenty Regional Council does not enforce the control of advisory species. It is landowner/occupier responsibility to manage these pests. Council may provide advice on how to manage or control these species if required.
How do you get rid of it?
- Small plants can be dug out, taking care to remove all of the larger roots and rhizomes, dispose of these carefully.
- Spray in spring when the leaves are young and soft with herbicide (Note: Do not spray over water).
- Cut and paint over leaf and flower stems with herbicide gel.
Dispose of any plant and root material at the refuse station in general waste. Continue treating new growth and pulling seedlings as they appear.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and directions for the purchase, use and storage of the product, are followed and adhered to.
Read more on pest control advice, information and regulations.