Family: Melastomataceae
Native to Brazil, Pleroma urvilleanum (syn. Tibouchina urvilleana) was introduced as an ornamental in 1910 to Kurtistown, Hawaiʻi Island. Only seven years later the superstar botanist/naturalist Joseph Rock reported it as naturalizing. A limited amount of seeds produced are viable, this invasive species mostly spreads vegetatively. The middle elevations on the wet sides of the state seem most prone to invasion. All 350 plants in the genus Tibouchina are on the Hawaiʻi State Noxious Weed List. 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 branched shrub up to 12 ft tall
- Hairy leaves (5 in long by 2 in wide) grow in an opposite pattern and have 5-7 prominent longitudinal veins from the base
- Large purple flowers (3-4 in) with 5 petals with sickle shaped purple anthers
- Cup shaped fruit is covered in hairs and filled with numerous spiral shaped seeds
- Spreads from root suckers, vegetatively and by seed.
High Risk Traits:
- High tropical/subtropical climate suitability
- Naturalized in Hawaii and New Zealand
- Naturalized on Kauaʻi, Maui, and Hawaiʻi; extirpated on Oʻahu
- Widely introduced and cultivated outside native range
- Forms dense, environmental weed thickets in wet Hawaiian habitats
- Congeneric species are noxious weeds
- Shade tolerant
- Spreads vegetatively via rooting branches
- Dispersed via garden debris and intentional human planting
- Tolerates pruning and regrows after damage
- Requires herbicides for effective control
Low Risk Traits:
- Non-toxic
- Lacks spines, thorns, or burrs
- Not allelopathic, parasitic, or fire-promoting
- No viable seed production in cultivated populations
- Not prolific seeder
- Not dispersed by wind, birds, animals, or gut passage
