Family: Melastomataceae

A herbaceous subshrub that spreads from initial plantings. It has light purple flowers and grows up to three feet. Native to southern Brazil, Uruguay, and Paraguay, Chaetogastra herbacea (syn. Tibouchina herbacea), commonly called cane tibouchina, was likely introduced to Hawai’i as an ornamental. In regards to beauty, this particular species does not hold a candle to other genus members. A poor choice for ornamental purposes, cane tibouchina, is called the least showy of all the glory bushes. There are unconfirmed reports of cane tibouchina naturalizing from 1977. That voucher went missing, so the first confirmed naturalization collection was from 1979 on Hawai’i Island.

Reports of locally abundant infestations occurred along Saddle rd. in 1982. By the early 1990s, this species began severely impacting Hawai’i Island’s wet and mesic forests. Other island infestations are somewhat recent, all accidental, likely from contaminated landscaping material and other human activities. In less than ten years, cane tibouchina went from locally abundant in Maui to widespread across all appropriate habitats. Each plant is capable of producing 3000 tiny seeds a year. Besides accidental dispersal through human activities, cane tibouchina seeds are dispersed by birds, rodents, pigs, and water. This self-compatible plant is shade tolerant and resprouts quickly after cutting or mutilation. The entire genus Tibouchina (now treated as multiple genera) is listed as noxious by the State of Hawaii. It is illegal to introduce this invasive species into areas “relatively free” of the harmful pest.

Description and Dispersal:

• A weakly branched herbaceous subshrub with light purple flowers growing up to 3 feet
  
• 4 sided stems becoming rounded with age
  
• Green leaves are blanketed in soft hair, have the classic Melastomataceae family venation-5 to 7 longitudinal veins, and are arranged opposite each other
  
• 4 pink petals and yellow large anthers are born from a floral cup
  
• Following flowers, seed capsules are born in their place.

High Risk Traits:

• Native to subtropical/tropical climates (Brazil, Uruguay, Paraguay); high climate match for invasion
  
• Naturalized on multiple Hawaiian Islands: O'ahu, Moloka'i, Lāna'i, Maui, and Hawai'i
  
• Invasive in forests, pastures, and waterways
  
• Unpalatable to cattle
  
• Tolerates shade (germinates and grows in closed-canopy forests)
  
• Tolerates poor soils (volcanic lava flows)
  
• Forms dense, monotypic thickets >3 m tall
  
• Self-compatible; produces viable seeds
  
• Reproduces vegetatively (rhizomes, rooting at nodes)
  
• Flowers within first year
  
• Dispersed by humans (roads/trails), intentional planting (ornamental), birds, and other animals (gut passage)
  
• Prolific seed production; persistent seed bank (>1 yr)
  
• Cutting promotes spread (vegetative regrowth)

Low Risk Traits:

• No spines, thorns, or burrs
  
• Non-toxic to animals and humans; no allergenic effects
  
• No allelopathic or parasitic behavior
  
• Not a fire hazard (prefers wet habitats)