Family: Poaceae

Origin, Description & Uses
Nassella cernua, commonly known as nodding needlegrass or foothill needlegrass, is a perennial bunchgrass native to California and northwestern Mexico. This grass is adapted to dry climates and open habitats, where it produces fine, arching leaves and distinctive nodding seed heads that give the plant its common name. It has been used in habitat restoration, erosion control, and native grass landscaping in parts of its native range because of its drought tolerance and ability to persist in poor soils.

Risks & Threats
Nassella cernua is naturalized in Hawaiʻi and possesses traits that are cause for concern in tropical island ecosystems. Like other invasive grasses, it can spread into disturbed areas, grasslands, and open natural habitats, where it may compete with native vegetation and alter ecosystem structure. Its ability to establish persistent populations and reproduce by seed increases the risk of further spread. Invasive grasses can also contribute to changes in fire behavior and ecosystem dynamics, potentially threatening biodiversity and sensitive native habitats. Because this species could detrimentally impact tropical island ecosystems, choosing a low risk or native alternative is recommended whenever suitable alternatives are available.

High Risk Traits:

• Grows in higher elevation tropical climates
  
• Naturalized on Hawaii island
  
• Weedy grass, with possible detrimental impacts to ranching
  
• Other Nassella species are invasive
  
• Tolerates many soil types
  
• Reproduces by seed
  
• Hybridizes with other Nassella species
  
• Self-compatible (cleistogamous)
  
• Seeds dispersed by wind, people and externally attached to animals
  
• Perennial, but able to reach maturity in <1 year
  
• Seeds able to be stored for extended periods; May form a persistent seed bank
  
• Resprouts after mowing and fires
  
• Limited ecological information may reduce accuracy of risk prediction

Low Risk Traits:

• May only be invasive at higher elevations
  
• Unarmed (no spines, thorns or burrs)
  
• Palatable to grazing animals
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control