Family: Alismataceae

Origin, Description & Uses
Sagittaria platyphylla (broad-leaf arrowhead, delta arrowhead) is an aquatic plant native to the central and eastern United States extending into Central America. It grows in shallow freshwater habitats such as ponds, marshes, and slow-moving streams. The plant produces distinctive broad, arrow-shaped leaves and can form both submerged and emergent growth depending on water conditions. It is sometimes used in ornamental water gardens and pond landscaping due to its attractive foliage and ability to grow in wet soils or shallow water environments.

Risks & Threats
On O‘ahu, this species is naturalized and continues to spread in freshwater systems. It reproduces readily through tubers and plant fragments, allowing it to establish dense stands that can crowd out native wetland plants, alter habitat structure, and reduce open water flow. These traits are cause for concern, as it can become invasive in suitable tropical island conditions and could detrimentally impact sensitive wetland and riparian ecosystems. When possible, choosing a low-risk or native alternative is strongly recommended. Where the species is already present, management or avoidance of use in areas where it is not yet widespread is important to minimize further spread and ecological harm in Hawai‘i’s freshwater habitats.

High Risk Traits:

• Can grow in warm temperate to tropical climates
  
• Naturalized in Australia, Oahu, Russia, Indonesia, South Africa and possibly elsewhere
  
• An agricultural weed (affecting irrigation) and an environmental weed (competing with native vegetation)
  
• Other Sagittaria species have become invasive
  
• Shade-tolerant
  
• Forms dense thickets in aquatic habitats
  
• Can spread from tubers or seeds
  
• Dispersed intentionally and unintentionally by people
  
• Seeds and vegetative fragments dispersed by water, in soil, by birds and in mud stuck to animals and machinery
  
• Prolific seed production
  
• Seeds and vegetative fragments may persist in the soil
  
• Tolerates cutting and will resprout without complete removal of plant, or treatment with herbicides
  
• Herbicide control is difficult due to aquatic nature of plants and poor translocation of herbicides to tubers or stolons

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Palatable to ducks and possibly other animals
  
• Non-toxic
  
• Ornamental