Family: Poaceae

Native to Africa, fountain grass (Cenchrus setaceus) was introduced to Hawaiʻi as an ornamental plant, although the exact date of introduction is unknown. By 1914, it had already escaped cultivation, and today it is widely established across the islands. Fountain grass is naturalized on Kauaʻi, Oʻahu, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island, and is considered potentially naturalizing on Molokaʻi. It thrives in dry, open habitats including barren lava flows and cinder fields, from about 40 to 2,140 meters (approximately 130–7,020 feet) in elevation. Its attractive, feathery flower plumes once made it a popular landscape plant, but it has since become one of Hawaiʻi’s most damaging invasive grasses.

Fountain grass is an aggressive invader that forms dense, monotypic stands across dry areas of the state, crowding out native vegetation and altering entire ecosystems. It disrupts the slow natural succession of lava fields into native forest and has transformed once-diverse dry forests into near single-species grasslands. In Kona, hillsides once known for rich native dry forest diversity and the striking yellow flowers of halapepe are now often dominated almost entirely by fountain grass. The species also creates a major fire hazard by producing continuous, highly flammable fuel loads that threaten both natural ecosystems and developed areas. Due to these impacts, Cenchrus setaceus is listed on the Hawaiʻi State Noxious Weed List and has been designated by the Hawaiʻi Department of Land and Natural Resources Division of Forestry and Wildlife as one of Hawaiʻi’s Most Invasive Horticultural Plants.

Description and Dispersal:

• Medium-sized clumping grass, grows up to 3 ft tall
  
• Leaves are long and round like wire, they do not form flat 'blades'
  
• The flower seedheads are long, purple to yellow 'spikes' (4 - 9.5 in)
  
• Seeds spread by the wind

High Risk Traits:

• Naturalized outside native range (including on Kaua‘i, O‘ahu, Lāna‘i, Kaho‘olawe, Maui, and Hawai‘i; potentially naturalizing on Moloka‘i)
  
• Weedy races exist (normal form)
  
• Environmental and agricultural weed
  
• Congeneric weeds present
  
• Unpalatable to grazers
  
• Creates fire hazard
  
• Tolerates wide range of soils
  
• Produces viable, apomictic seeds
  
• No specialist pollinators needed
  
• Reproductive in 1 year
  
• Dispersed unintentionally (vehicles, humans, livestock)
  
• Dispersed intentionally (ornamental trade)
  
• Dispersed as contaminant, wind, water, externally by animals
  
• Persistent seed bank (≥6 years)
  
• Fire-adapted

Low Risk Traits:

• No spines, burrs, or thorns
  
• Not toxic to animals or humans
  
• Not shade tolerant
  
• No vegetative spread