Family: Apocynaceae

Origin, Description & Uses:
Calotropis procera, commonly known as small crownflower, purple crownflower, or rubber bush, is a shrub or small tree native to the arid and semi-arid regions of Africa, the Middle East, and South Asia. It is characterized by thick gray-green leaves, milky white sap, and clusters of waxy, star-shaped flowers that are pale lavender to white with purple centers. Highly tolerant of drought, heat, and poor soils, it thrives in dry coastal and disturbed habitats. In other parts of the world, it has been grown as an ornamental, used as a living fence, and valued for traditional medicinal purposes, while its bark fibers and silky seed floss have been used for making cordage, stuffing, and other products.

Risks & Threats:
Small crownflower is naturalized on Kauaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi Island, and is potentially naturalizing on Oʻahu. It possesses several traits that are cause for concern, including prolific production of wind-dispersed seeds, rapid establishment, drought tolerance, and the ability to thrive in harsh, disturbed environments. These characteristics allow it to spread into dry and coastal ecosystems, where it can outcompete native vegetation and alter natural plant communities. Because this species is already established on multiple Hawaiian Islands and could further detrimentally impact tropical island ecosystems, planting it is not recommended. Where possible, choose a low-risk or native alternative. In areas where small crownflower is already widespread, avoid planting it in new locations and manage existing plants to prevent additional spread into natural areas.

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