Family: Apocynaceae

Calotropis procera, commonly known as small crownflower, purple crownflower, or rubber bush, is a shrub or small tree native to arid regions of Africa, the Middle East, and South Asia. It has thick, gray-green leaves, milky sap, and showy, waxy flowers that are typically pale lavender to white with purple centers. Well adapted to dry, hot conditions, small crownflower is tolerant of poor soils and drought. In other parts of the world it has been used ornamentally, as a living fence, and in traditional medicine, and its fibrous bark and silky seed floss have been used for cordage and stuffing.

Despite its attractive flowers and toughness, small crownflower poses significant risks in Hawai‘i. This species has the potential to become a noxious weed, as it has in other regions, where it spreads aggressively and displaces native vegetation, particularly in dry and disturbed landscapes. Its abundant wind-dispersed seeds, rapid growth, and tolerance of harsh conditions make it difficult to control once established. For these reasons, homeowners are discouraged from planting small crownflower in any situation where it might escape from cultivation. Preventing its spread is important to protect Hawai‘i’s unique ecosystems and reduce future management challenges.

High Risk Traits:

• Naturalized globally
  
• Agricultural weed (forms thickets, reduces pasture quality)
  
• Toxic to humans (skin irritant, poisonous)
  
• Forms dense thickets
  
• Reproduces vegetatively (root suckers)
  
• Contaminates crops and hay
  
• Wind and water dispersed
  
• High seed production
  
• Persistent seed bank
  
• Resprouts after cutting/burning

Low Risk Traits:

• Not shade tolerant
  
• Not self-compatible
  
• Not bird-dispersed