Family: Myrtaceae

An invasive tree that is invading moist forests. Native to Brazil and commonly known as waiwi, P. cattleianum was introduced to Hawaiʻi in 1825. Widely planted, waiwi is aggressively replacing diverse native forests. The single-species waiwi forests are incredibly muddy, full of mosquitoes, and fruit flies. It is nothing like a healthy forest with multiple forest layers, a thick mat of ferns, and vegetative debris on the forest floor.

If left unchecked, this forest menace has the potential to invade almost half the conservation lands on Hawaiʻi Island, amounting to 300,000 acres. This species is found on all the main Hawaiian Islands. The Division of Forestry and Wildlife of the Hawaiʻi Department of Land and Natural Resources has designated this species as one of “Hawaiʻi’s Most Invasive Horticultural Plants.”

Description and Dispersal:

• A tree up to 20 ft tall with smooth reddish bark
  
• Shiny leathery leaves (4 in long by 2.5 in wide) that grow opposite
  
• White flowers (less than 1 in); numerous round red or yellow fruit (1 in)
  
• Seeds spread by birds and pigs

High Risk Traits:

• Naturalized and invasive in tropical/subtropical regions (Hawaii, Tahiti, Réunion, Mauritius)
  
• Environmental weed; forms dense, monotypic stands
  
• Congeneric weed (P. guajava is a serious pest)
  
• Allelopathic (inhibits other plants)
  
• Shade tolerant
  
• Reproduces by seed and vegetative suckers
  
• Self-fertile
  
• Prolific seed producer (25–70 seeds/fruit)
  
• Seeds dispersed by birds, pigs, and humans (including gut passage)
  
• Tolerates mutilation (vigorous regrowth from cut stumps)

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not toxic to animals or humans
  
• No evidence of fire hazard
  
• No persistent seed bank (>1 year)
  
• Well-controlled by several herbicides (e.g., Garlon 4, glyphosate)