Family: Poaceae

Origin, Description & Uses
Dactylis glomerata, commonly known as orchard grass or barnyard grass, is a cool-season perennial grass native to Europe, North Africa, and parts of temperate Asia. It has been widely introduced around the world as a valuable forage species for livestock due to its rapid growth, high nutritional value, and tolerance of a range of soil conditions. Orchard grass forms dense clumps with upright stems and distinctive tufted seed heads. In Hawaiʻi, it has become naturalized on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi Island, particularly in cooler, upland pastures and disturbed areas.

Risks & Threats
Although orchard grass is useful in agricultural settings, it is naturalized in Hawaiʻi and possesses traits that are cause for concern. It grows quickly, produces abundant seed, and can form dense stands that compete with native vegetation. In higher elevation and mesic environments, it may displace native grasses and understory plants, altering plant community structure and reducing habitat quality for native species. Its persistence and ability to spread along roadsides, pastures, and disturbed lands mean it could detrimentally impact tropical island ecosystems if not carefully managed. Preventing further spread and avoiding planting near sensitive natural areas is recommended.

High Risk Traits:

• Elevation range exceeds 2000 m, demonstrating environmental versatility
  
• Grows in temperate and tropical climates
  
• Widely introduced and naturalized, including Kauai, Oahu, Molokai, Maui, and Hawaii
  
• Disturbance-adapted environmental weed
  
• Pollen is allergenic
  
• Shade-tolerant
  
• Tolerates many soil types
  
• Forms dense swards
  
• Reproduces by seeds
  
• Self-compatible
  
• Able to reach maturity in <1 year
  
• Seeds dispersed by wind, as a contaminant, attached to animals or internally, and intentionally planted
  
• Prolific seed production (densities unknown)
  
• Able to resprout after cutting or fire

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Highly palatable to grazing animals
  
• Non-toxic
  
• Not reported to spread vegetatively
  
• Does not form a persistent seed bank
  
• Herbicides may provide effective control