Family: Sphagnaceae

Origin, Description & Uses
Sphagnum palustre (peat moss, boat-leaved sphagnum) is a moisture-loving moss native to wetland and bog habitats in many parts of the world. In Hawaiʻi, it is indigenous to the Kohala region of Hawaiʻi Island and was intentionally introduced in the 1960s to what is now the Kaʻala Natural Area Reserve on Oʻahu. This soft, spongy moss forms dense mats that can hold large amounts of water, helping regulate moisture in wetlands and cloud forests. Around the world, peat moss species are widely used in horticulture, landscaping, and plant propagation because of their exceptional water-retention properties.

Risks & Threats
Although Sphagnum palustre is indigenous to portions of Hawaiʻi Island, it has been introduced outside of its native Hawaiian range and is now naturalized on Oʻahu. This species possesses traits that are cause for concern, including rapid vegetative spread and the ability to form thick carpets that alter habitat conditions. Dense moss mats can modify hydrology, nutrient cycling, and vegetation structure, potentially affecting native plant communities and sensitive wetland ecosystems. Because tropical island ecosystems are especially vulnerable to ecological changes caused by introduced species, the spread of S. palustre beyond its native range may have detrimental impacts. Where possible, low-risk or native alternatives should be selected for landscaping, restoration, or horticultural uses. In areas where this species is already established, efforts should focus on preventing further spread into new locations and protecting sensitive native habitats.

High Risk Traits:

• A predominantly temperate species, but able to grow in higher elevation tropical islands
  
• Naturalized on Oahu and outside natural range on Hawaii island
  
• An environmental weed on Oahu (Hawaiian Islands), smothering the ground and threatening native plant regeneration
  
• Allelopathic
  
• Unpalatable to browsing and grazing animals
  
• Shade-tolerant
  
• Forms dense mats that exclude native vegetation
  
• Reproduces by spores and vegetatively
  
• Able to reproduce rapidly
  
• Dispersed along trails by human activity
  
• Spores dispersed by wind and possibly water
  
• Intentionally spread by people, and unintentionally spread in planting materials
  
• Able to recover from trampling and mechanical control

Low Risk Traits:

• May be limited to cooler, higher elevation areas with sufficient moisture
  
• Unarmed (no spines, thorns, or burrs)
  
• Non-toxic
  
• Dioecious (may limit sexual reproduction)
  
• Chemical control methods have proven effective