Family: Cyperaceae

Origin, Description & Uses
Rhynchospora caduca (anglestem beak sedge or beak rush) is native to the southeastern and central United States, where it occurs in wetlands, marshes, and other seasonally wet habitats. It is a grass-like sedge that typically grows in clumps in wet, disturbed ground, often at mid-elevations in Hawaiʻi (approximately 320–1,400 m). In the Hawaiian Islands, it has been recorded on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, where it is found sparingly in wet areas. It has no major known economic or ornamental uses locally and is primarily encountered in natural or disturbed wetland environments.

Risks & Threats
This species is now naturalized in Hawaiʻi and possesses traits that are cause for concern, particularly its ability to establish in wet, disturbed habitats and spread through seed production. In suitable conditions, it may form dense stands that compete with and displace native wetland plants, potentially altering habitat structure and ecological function in sensitive tropical island ecosystems. Because it is already present across multiple islands, continued spread into new wetland areas remains a concern. Where available, choosing low-risk native or non-invasive alternatives is recommended. In areas where it is not yet widely established or is still localized, managing populations and preventing further planting or spread can help reduce additional impacts to Hawaiʻi’s wetland ecosystems.

High Risk Traits:

• Elevation range exceeds 1000 m, demonstrating environmental versatility
  
• Thrives in tropical climates
  
• Naturalized on Kauai, Oahu, Molokai, Maui, and Hawaii (Hawaiian Islands)
  
• Disturbance-adapted weed with negative environmental impacts in native forest
  
• Other Rhynchospora species have become invasive
  
• Unpalatable to grazing animals
  
• Reproduces by seeds and possibly by rhizomes
  
• Seeds dispersed externally and by water
  
• Limited ecological information may limit accuracy or risk assessment

Low Risk Traits:

• Unarmed (no spines, thorns, or burrs)
  
• Non-toxic