Family: Gunneraceae

Origin, Description & Uses:
Gunnera manicata, commonly known as Brazilian giant-rhubarb, is a dramatic, herbaceous plant native to southeastern Brazil. It is best known for its enormous, umbrella-like leaves that can grow several feet across, giving it a bold, tropical appearance in landscapes and botanical gardens. This species thrives in moist, nutrient-rich soils and is often planted near ponds or water features as an ornamental focal point. Despite its common name, it is not a true rhubarb and is grown strictly for decorative purposes rather than for food.

Risks & Threats:
Although Brazilian giant-rhubarb is not currently known to be naturalized in the Hawaiian Islands, it possesses traits that raise serious concerns. It can spread aggressively through both seeds and vegetative growth, forming dense colonies that outcompete and displace native vegetation. In other parts of the world with similar climates, it has shown the ability to invade wetlands and riparian areas, altering habitat structure and ecosystem function. Its large leaves can also shade out smaller plants, reducing biodiversity. Because of these high-risk characteristics, introducing or planting this species in Hawai‘i could negatively impact sensitive tropical island ecosystems. It is strongly recommended to choose a low-risk or native alternative for landscaping to help protect Hawai‘i’s unique environment.

High Risk Traits:

• Broad climate suitability
  
• Naturalized outside native range
  
• Congeneric weed
  
• Produces spines/thorns/burrs
  
• Tolerates wide range of soils
  
• Prolific seed production (>1000/m²)
  
• Intentionally dispersed by people
  
• Not easily controlled by herbicides

Low Risk Traits:

• Not wind or water dispersed