Family: Apocynaceae

Origin, Description & Uses: Cryptostegia grandiflora (rubber vine, purple allamanda) is a fast-growing woody vine native to Madagascar. It is known for its showy, trumpet-shaped purple to pink flowers and glossy green leaves, making it an attractive ornamental plant in warm climates. This vigorous climber produces long twining stems that can scramble over fences, trees, and structures, and it exudes a milky latex historically used in rubber production. Because of its lush appearance and drought tolerance, it has been planted in tropical landscapes, including parts of Hawai‘i, where it is now naturalized on O‘ahu.

Risks, Threats & Management: This species is naturalized and possesses traits that are cause for concern. Rubber vine grows rapidly, forms dense mats that smother vegetation, and produces abundant wind-dispersed seeds that enable it to spread into natural areas. In tropical island ecosystems, it has the potential to overtop native plants, alter habitats, and reduce biodiversity if not carefully managed. Its vigorous growth and ability to invade disturbed and dry environments increase the risk of ecological impacts. Due to these concerns, it is recommended to choose a low-risk or native alternative for landscaping to help protect Hawai‘i’s unique ecosystems.

High Risk Traits:

• Invasive & naturalized globally in tropics/subtropics (including O'ahu)
  
• Forms dense thickets, smothers native vegetation
  
• Climbs and overtops trees
  
• Shade tolerant
  
• Tolerates wide soil types
  
• High seed production (>1000/m²)
  
• Seeds dispersed by wind, water, animals, humans
  
• Toxic to livestock and humans
  
• Unpalatable to grazers
  
• Increases fire hazard
  
• Resists control (regrows after cutting)
  
• Hybridizes with related species
  
• No effective natural enemies in invaded areas
  
• Causes major economic losses
  
• Displaces native species, reduces biodiversity

Low Risk Traits:

• No spines/thorns
  
• Not allelopathic or parasitic
  
• Requires specialist pollinators
  
• No known reproductive failure in native range
  
• Short-lived seed bank (<1 year)
  
• Controllable with herbicides
  
• Climate limited to tropics/subtropics