Family: Poaceae

Chasmanthium latifolium, commonly known as northern sea oats or inland sea oats, is a perennial ornamental grass native to the eastern and central United States. It is best known for its distinctive, flat, oat-like seed heads that dangle from arching stems and turn from green to bronze as they mature. Northern sea oats is widely planted in landscapes and gardens for its attractive texture, ability to thrive in shade, and tolerance of a range of soil conditions. It is often used for erosion control, naturalistic plantings, and cut or dried floral arrangements.

Although Chasmanthium latifolium is not currently known to be naturalized in Hawaiʻi, it possesses several traits that raise concern. The species produces abundant seed, spreads readily under favorable conditions, and tolerates shade and disturbance—characteristics that can give it a competitive advantage outside its native range. In tropical island ecosystems, these traits could allow it to escape cultivation, form dense stands, and displace native understory plants. Because island ecosystems are particularly vulnerable to invasion, further evaluation is warranted to determine whether northern sea oats could pose detrimental impacts if introduced or more widely planted.

High Risk Traits:

• Garden/amenity weed potential
  
• Self-sows readily, can be invasive in cultivation
  
• Produces abundant viable seed
  
• Self-compatible, spreads via rhizomes
  
• Short generation time (~1 year)
  
• Broad climate tolerance (Zones 4–9)
  
• Shade tolerant, wide soil tolerance
  
• Forms dense stands/monocultures
  
• Wind and water dispersed seeds
  
• Horticultural trade increases spread

Low Risk Traits:

• Not invasive outside native range
  
• Not naturalized beyond native range
  
• Not an agricultural/environmental weed
  
• Non-toxic to animals/humans
  
• Non-allelopathic, non-parasitic