Family: Myrtaceae

Origin, Description & Uses:
Psidium guajava, commonly known as common guava, is a small tropical tree native to the Neotropics that has been widely cultivated throughout tropical and subtropical regions for its edible fruit. It was likely introduced to Hawaiʻi in the early 1800s and is now naturalized on nearly all of the main Hawaiian Islands. Guava produces fragrant white flowers and round to pear-shaped fruits with sweet, aromatic flesh that are eaten fresh or used in juices, jams, desserts, and other food products. The tree is also grown as a backyard fruit tree and for shade in tropical landscapes. In Hawaiʻi, common guava is now frequently found in disturbed dry, mesic, and wet forests from low to mid elevations, where it often forms dense stands.

Risks & Threats:
Common guava is naturalized in Hawaiʻi and possesses several traits that are cause for concern in tropical island ecosystems. It grows rapidly, produces abundant fruit that is readily spread by birds, pigs, and other animals, and can form dense thickets that crowd out native vegetation and hinder forest regeneration. These dense stands may alter habitat structure, reduce native biodiversity, and contribute to the spread of invasive animals that feed on the fruit. Because of its invasive tendencies and ability to spread into natural areas, common guava could further detrimentally impact tropical island ecosystems if unmanaged. When possible, choose a low risk or native alternative for landscaping and fruit production. In areas where common guava is already widespread, avoid planting it near natural areas and manage existing populations to help minimize further spread and negative ecological impacts.

High Risk Traits:

• Naturalized across tropics/subtropics
  
• Naturalized on Kauaʻi, Oʻahu, Molokaʻi, Lanaʻi, Maui, and Hawaiʻi
  
• Forms dense thickets in forests and disturbed areas
  
• Serious environmental weed (Galapagos, Pacific islands)
  
• Agricultural weed in pastures; difficult to eradicate
  
• Congeneric (P. cattlenianum) is weedy
  
• Allelopathic (leaves, root exudates inhibit other plants)
  
• Host to 222 fungi + guava fruit fly
  
• Self-compatible (60–75% self-pollination)
  
• Prolific seed production (100+ seeds/fruit; year-round fruiting)
  
• Seeds survive gut passage (birds, pigs, cattle, horses)
  
• Dispersed intentionally by humans (edible fruit) and unintentionally along trails
  
• Tolerates fire (resprouts from base)
  
• Broad climate and soil tolerance

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not toxic to animals or humans (medicinal uses)
  
• Not shade tolerant
  
• No persistent seed bank (viable only several months)
  
• Not adapted to wind or water dispersal
  
• Seeds too large for produce contaminant