Family: Gunneraceae

Origin, Description & Uses:
Gunnera tinctoria, commonly known as Chilean rhubarb or giant rhubarb, is a striking perennial plant native to southern South America, particularly Chile and Argentina. It is known for its enormous, umbrella-like leaves that can grow several feet across, forming dense, lush clumps in moist environments. This species thrives in wetlands, along streambanks, and in other areas with abundant water. Due to its dramatic size and bold appearance, it is sometimes used as an ornamental plant in large gardens and landscapes. Despite its common name, it is not closely related to true rhubarb, though its leaf stalks have occasionally been used in culinary applications after proper preparation.

Risks & Threats:
Although Gunnera tinctoria is not currently known to be naturalized in the Hawaiian Islands, it possesses several traits that raise concern for tropical ecosystems. It spreads aggressively through both seeds and vegetative growth, forming dense stands that can outcompete native vegetation, alter hydrology, and reduce biodiversity. In regions where it has become invasive, such as parts of Europe and New Zealand, it has proven difficult to control once established. Its preference for wet habitats makes sensitive areas like streams, wetlands, and forest margins particularly vulnerable. Because of these risks, planting Gunnera tinctoria is not recommended in Hawaii. Instead, consider choosing a low-risk or native alternative to help protect the health and resilience of island ecosystems.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Native to and naturalized in regions with a temperate and Mediterranean climate (could threaten upper elevations of tropical and subtropical islands)
  
• Naturalized in the Azores, New Zealand, Ireland, the UK, France, and California (but no evidence in the Hawaiian Islands to date)
  
• An environmental weed in New Zealand and Ireland, reducing native biodiversity
  
• Gunnera manicata is also invasive
  
• Leaves covered with stiff prickles
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Forms dense stands that exclude other vegetation
  
• N-fixing (may alter soil chemistry)
  
• Reproduces by seeds and vegetatively by rhizomes (able to spread by rhizome fragments)
  
• Seeds dispersed by birds, water, as a soil contaminant and intentionally by people
  
• Rhizome fragments also moved by water
  
• Prolific seed production
  
• Seeds may form a persistent seed bank (reports from New Zealand suggest no seed bank is formed, but UK evidence suggests yes)
  
• Able to resprout after cutting

Low Risk Traits:

• Climate preferences may limit invasiveness to upper elevations of tropical islands
  
• Palatable to browsing and grazing animals (does not spread into pastures with livestock)
  
• Reaches maturity in 4-5 years (but may be able to spread vegetatively at an earlier age)
  
• Herbicides may provide effective control