Family: Poaceae

Origin, Description & Uses
Cenchrus purpureus (red fountain grass, elephant grass, banagrass) is a large, fast-growing perennial grass native to Africa and parts of the Arabian Peninsula. It is widely cultivated in tropical and subtropical regions as forage for livestock, erosion control, windbreaks, and biomass production. This tall grass can form dense clumps reaching several meters in height, with broad leaves and thick cane-like stems. In Hawaiʻi, it was first documented on Lānaʻi in 1922 after being introduced through agricultural plantings, and it has since become naturalized on Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island. It is commonly found in fields, pastures, roadsides, and other mesic to wet habitats across a wide elevational range.

Risks & Threats
Although valued as a forage and utility grass, Cenchrus purpureus is naturalized in Hawaiʻi and possesses traits that are cause for concern in tropical island ecosystems. Its vigorous growth, ability to spread rapidly, and tendency to form dense stands can displace native vegetation and alter habitat structure. The species may also increase fuel loads and contribute to fire risk in invaded landscapes. Once established, it can be difficult to control because of its robust root system and ability to regrow after cutting or disturbance. Due to its invasive potential and capacity to negatively impact sensitive ecosystems, planting this species is discouraged near natural areas. When possible, choose a low-risk or native alternative better suited for Hawaiʻi’s unique environments.

High Risk Traits:

• Naturalized in multiple regions (Florida, Hawaii, American Samoa)
  
• Naturalized across all main Hawaiian Islands (Kaua‘i, O‘ahu, Moloka‘i, Lana‘i, Kaho‘olawe, Maui, and Hawai‘i)
  
• Agricultural weed (Colombia, Ghana, Mozambique, Trinidad)
  
• Environmental weed (Florida wildland invader)
  
• Congeneric weeds exist
  
• Forms dense, impenetrable thickets
  
• Tolerates wide range of soil conditions (poorly drained to dry sandy soils)
  
• Reproduces vegetatively (stolons, rhizomes)
  
• Self-compatible or apomictic
  
• Propagules dispersed intentionally (pasture grass, ornamental), as produce contaminant, and by wind
  
• Regrows after clipping/mowing; resprouts from rhizomes
  
• Tolerates fire

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not allelopathic or parasitic
  
• Not toxic to animals (except rare nitrate poisoning from high-N soil)
  
• No major pest/pathogen host
  
• Shade intolerant
  
• Limited seed production; no persistent seed bank
  
• Controlled by herbicides