Family: Zingiberaceae

Alpinia zerumbet, commonly known as shell ginger, is a perennial herb native to East Asia. In Hawai‘i, it has become naturalized across several islands. On Kaua‘i, O‘ahu, Moloka‘i, and Maui, shell ginger has established itself in various habitats, including moist forests and shaded areas near streams. Its presence is noted for forming dense thickets, particularly in wet environments, which can impact local ecosystems by outcompeting native vegetation. The plant reproduces both by rhizome division and by producing numerous seeds that are dispersed by birds and water, facilitating its spread in suitable habitats.

On Lana‘i, shell ginger is potentially naturalizing, indicating that while it has been introduced, it has not yet fully established self-sustaining populations. Despite its ornamental appeal, shell ginger is considered a high-risk species in Hawai‘i due to its invasive potential and the challenges it poses to native ecosystems. Efforts to manage its spread are important to preserve the integrity of local habitats and biodiversity.

High Risk Traits:

• Highly Adaptable: Tolerates a wide range of climates, altitudes, and soil types.
  
• Naturalized Invader: Documented as naturalized in multiple regions (e.g., Hawaii, South Africa, Puerto Rico).
  
• Forms Monocultures: Creates dense, monotypic thickets that crowd out native vegetation.
  
• Prolific Reproduction: Spreads effectively via both bird-dispersed seeds (producing >1000/m²) and vegetative rhizomes.
  
• Multiple Dispersal Pathways: Seeds are dispersed by birds and water (along streams).
  
• Resilient: Resprouts vigorously after damage, frost, or cutting.
  
• Widely Introduced: Has a long history of repeated ornamental introductions worldwide.

Low Risk Traits:

• Not Toxic: No evidence of toxicity to animals or humans.
  
• No Physical Defenses: Lacks spines, thorns, or burrs.
  
• Not a Host: Not a significant host for major pests or pathogens.
  
• Not a Fire Hazard: Succulent nature does not increase fire risk.
  
• Limited Accidental Spread: Seeds lack mechanisms for wind dispersal or attachment to animals/equipment.
  
• Not a Contaminant: Seeds are large and unlikely to be a produce contaminant.