Family: Poaceae

Urochloa decumbens (signal grass, Surinam grass) is a perennial grass native to Africa. It is cultivated as forage grass and used for erosion control on hillsides. It is now widespread in the tropics and subtropics, and is reported to be naturalized on Kauai, Oʻahu, Molokai, Kahoʻolawe, and Hawaiʻi. Urochloa decumbens can exhibit invasive characteristics such as rapid growth, prolific seed production, and resilience to grazing. In some areas, it may displace native vegetation and alter ecosystems, making its management important to prevent unwanted spread.

High Risk Traits:

• Broad climate suitability
  
• Thrives and spreads in regions with tropical climates
  
• Naturalized on Kauai, Oahu, Molokai, Kahoolawe, Hawaii (Hawaiian Islands) and elsewhere
  
• A weed of gardens, parks, roadsides, disturbed sites, waste areas, creek-banks (i.e., riparian areas), open woodlands and plantation crops
  
• An environmental weed, impacting native vegetation in Brazil and Australia
  
• Other Urochloa species are invasive
  
• Allelopathic
  
• Potentially toxic or harmful to grazing animals under certain growing conditions
  
• Tolerates many soil types
  
• Forms a dense cover that can exclude other vegetation
  
• Reproduces by seeds and stolons
  
• Apomictic
  
• Seeds dispersed by water, animals, as a produce contaminant, by ants, and intentional cultivation
  
• Prolific seed production
  
• Tolerates heavy grazing and fire

Low Risk Traits:

• Despite naturalization, negative impacts have not been reported from the Hawaiian Islands to date
  
• Unarmed (no spines, thorns, or burrs)
  
• Palatable to grazing animals
  
• Seeds lose viability after 5 months (do not form a persistent seed bank)
  
• Herbicides may provide effective control