Also known as
Brazilian rhubarb, gunnera chilensis, G. scabra, gunnera, giant rhubarb
Where is it originally from?
What does it look like?
Large, clump-forming, summer-green herb (<2 m) growing from stout horizontal rhizomes. Massive, rough and wrinkled umbrella-sized leaves (80 cm x 1 m) on sturdy stalks have 5-7 lobes and raised veins beneath. Both leaves and leaf stalks are covered in rubbery red prickles. Dies down over winter in cold climates and grows new leaves in spring from large, lobed, scaly buds (25 cm long) that are pinkish-green when fresh and dry to brown. Tiny, densely packed green flowers (summer) on long, erect, conical spikes (<1 m long) rising from the base of the leaves develop into reddish, oblong fruit (1.5-2mm long), each containing a single oblong seed.
Are there any similar species?
Gunnera manicata has membranous webbing between the lobes and is also considered weedy in some areas.
Why is it weedy?
Grows into large plants that form dense colonies, and large leaves shade out and suppress native vegetation. Produces an abundance of viable seed (approximately 250,000 seeds in a year) and also spread by rapid rhizome growth, making it difficult to control.
How does it spread?
Seeds are spread by water and by birds. Spreads vegetatively by growth of rhizomes and regrowth from rhizome fragments.
What damage does it do?
Alters the habitat of birds, insects and lizards, can block drains and streams and obstruct access to natural and recreational areas, and contribute to erosion on slip-prone banks.
Which habitats is it likely to invade?
Requires moist soil and full sun to dappled shade in habitats such as coastal cliffs, forest, forest edges, river and stream banks, drains and wetlands.
What can I do to get rid of it?
1. Remove flower spikes and dispose at landfill (all year round).
2. Pull out seedlings (all year round).
3. Dig out individual plants or small patches (all year round): Ensure removal of all rhizome fragments and flower/seedheads and dispose of these at a refuse transfer station.
4. Cut and paint (spring): Cut off the leaves and paint the stalk stumps with picloram gel or glyphosate (250ml/L)
.5. Spray (full leaf and actively growing): glyphosate (10ml/L knapsack)