Family: Myrtaceae

Origin, Description & Uses
Syzygium cumini (Java plum, jamun) is a large, evergreen tree native to tropical and subtropical Asia through northern Queensland, Australia. It is valued for its dense shade, glossy foliage, fragrant flowers, and edible purple-black fruits, which are eaten fresh and used in beverages, preserves, and traditional medicines. Because of its attractive appearance and useful fruit, Java plum has been widely planted as an ornamental, shade, and food-producing tree in tropical regions around the world. In Hawaiʻi, it has been cultivated for many years and is now naturalized on Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island. It is commonly found in mesic valleys, disturbed forests, and other moist habitats from approximately 40 to 1,230 meters elevation.

Risks & Threats
Java plum is naturalized in Hawaiʻi and possesses traits that are cause for concern. The species produces abundant fruit that is readily dispersed by birds, bats, and other animals, allowing it to spread far from cultivation sites. Seedlings can establish in disturbed areas as well as intact natural habitats, where dense stands may develop and compete with native vegetation for light, space, water, and nutrients. Its ability to thrive in a variety of environmental conditions and form self-sustaining populations could detrimentally impact tropical island ecosystems by altering forest structure and reducing native biodiversity. Because this species is already widespread in Hawaiʻi, efforts should focus on managing existing populations and preventing its use in areas where it is not yet widely established. When selecting trees for landscaping or restoration projects, choose a low-risk or native alternative whenever suitable options are available.

High Risk Traits:

• Broad climate suitability, including tropical and subtropical regions
  
• Thrives in a wide range of soil conditions
  
• Tolerates drought, waterlogging, and frost
  
• Naturalized outside its native range, including in Hawaii and other Pacific islands
  
• Naturalized on all main Hawaiian Islands except Niʻihau and Kahoʻolawe (Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi)
  
• Acts as a landscape nuisance and competes with other plants
  
• Classified as an environmental weed that forms dense, shade-casting canopies
  
• Listed as a threat to biodiversity, with planting banned in some regions
  
• Congeneric species are known to be invasive
  
• Produces viable seeds that are readily dispersed by birds and mammals
  
• Seeds can survive passage through the gut of animals
  
• Able to regenerate and resprout after cutting (coppices)
  
• Shade-tolerant at the seedling stage

Low Risk Traits:

• No spines, thorns, or burrs
  
• Palatable to grazing animals, with no known toxicity
  
• Reproduces by seed, with no evidence of vegetative spread
  
• Produces relatively large seeds, unlikely to reach densities >1000/m²
  
• Seeds are recalcitrant and do not form a long-lived persistent seed bank
  
• No evidence of external dispersal mechanisms (e.g., hooks, barbs)
  
• Susceptible to herbicides and can be managed through manual removal
  
• Considered resistant to the fungal pathogen Austropuccinia psidii, which is present in Hawaii