Other common names: Chilean rhubarb, giant rhubarb
Giant gunnera / Chilean rhubarb, giant rhubarb
Why it is a pest plant
|Production threat||Environmental threat||Public threat|
Giant gunnera is an invasive large clump-forming herbaceous plant which forms dense patches that exclude virtually all other plants. It has stout rhizomes (large, fleshy underground stems) and massive umbrella-sized leaves. Overall the plant resembles a giant common rhubarb plant. The plant grows vigorously during spring and early summer, forming new stems, leaves and up to five yellow flower spikes which rise from the base of the leaves. G.manicata (up to 3m high) is larger than G.tinctoria (up to 2m high).
- In summer, tiny green flowers are formed on a large spike up to 1m long.
- Flowers are followed by tiny fruit.
- It produces abundant tiny red fruit, which are spread by birds.
- Each spike can produce up to 80,000 seeds per head.
- Its leaves have 5-7 lobes and are hairy beneath, especially on the veins.
- G.tinctoria leaves are up to 1m across while G.manicata leaves can be up to 2m across.
- Both resemble rhubarb leaves in shape.
- Leaves and stems are covered in rubbery prickles.
Giant gunnera was introduced to New Zealand from South America for its interesting form and now has moved from the garden to the wild. Giant gunnera can shade out other plants and take over whole areas of both native habitat and pasture land. In the Taranaki region it has aggressively invaded a number of areas, forming dense stands and spreading to bluffs,wet cliffs and several waterways. In the Waikato this plant is showing the same pattern as Taranaki, so acting sooner rather than later to remove and control this pest plant will help us to avoid a similar spread happening here.
Giant hogweed (Heracleum mantegazzianum) looks similar to (but should not be confused with) giant gunnera. Giant hogweed’s leaves are more deeply lobed. It has tall flower stalks with large umbrella-like clusters of greenish-white flowers.
Responsibility for control
All landowners/occupiers in the Waikato are responsible for the control of giant gunnera on their property. All landowners/occupiers in the Waikato are responsible for controlling giant gunnera on their properties. Giant gunnera is also banned from being sold, propagated, distributed or included with commercial displays.
How to control giant gunnera
Pull out seedlings and dig out individual plants or small patches, ensuring all rhizome fragments, flower heads and seed heads are removed and disposed of at a refuse transfer station.
Cut stump treatment
For small patches, dig out, taking care to get all root parts OR cut right back and treat the stumps with a concentrated herbicide in gel form. Bury discarded seed heads and rhizomes deeply or take them to a landfill. Other parts can be composted.
For large patches, cut the plant right down to 10-20cm stumps then apply herbicide concentrate (see summary of herbicides). Repeat in the following season where necessary.
For large patches, cut off the flower heads to prevent further seed dispersal and then spray the leaves well while in full foliage with a herbicide (see summary of herbicides).
Safety when using herbicides
- Follow the instructions on the manufacturer’s label.
- Always wear protective clothing.
- Always minimise the risk to your other plants.
- Contact the supplier for further advice.
Summary of herbicides and application methods for control
|Triclopyr plus penetrant||Cut stump treatment, spray application.|
|Triclopyr/picloram mix plus penetrant||Cut stump treatment, spray application.|
|Metsulfuron plus penetrant||Cut stump treatment, spray application.|
|Glyphosate plus penetrant||Cut stump treatment, spray application.|
|Glyphosate gel||Cut stump treatment.|
|Picloram gel||Cut stump treatment.|
|Herbicide rules will apply. You may need to notify neighbours if spraying. The Waikato Regional Plan explains the agrichemical (herbicides) use rule in section 6.2|
|If applying herbicide over water, a resource consent may be required. Please check with Waikato Regional Council before you begin.|
- For advice and additional information on control methods, call our pest plant staff on freephone 0800 BIOSEC (0800 246 732).
- Chemical company representatives, farm supply stores and garden centres can also be good sources for advice.
View, download or order the following publications or call our freephone 0800 800 401.
- National Pest Plant Accord (Manual of plants banned from sale, propagation and distribution) ($10.00 plus GST)
- Plant Me Instead! (Plants to use in place of common pest plants) (free)
- Waikato Regional Pest Management Plan (RPMP) (free) (Section 5.23, page 83)
- Waikato Regional Council pest guide (free)