Family: Apocynaceae

Origin, Description & Uses
Strophanthus amboensis is native to a broad region of central and southern Africa, ranging from the Democratic Republic of the Congo to northern-central Namibia. It is a climbing woody vine or liana that produces showy, often fragrant, tubular flowers. Like other members of the genus, it is adapted to forest edges and woodland habitats, where it can climb over shrubs and trees for support. The plant is sometimes cultivated in botanical or ornamental collections for its striking flowers and vigorous climbing habit. The genus Strophanthus is also historically notable for its production of potent cardiac glycosides, compounds that have been used in traditional medicine and, in some contexts, as arrow poisons. While not widely used horticulturally, it may be grown by specialty plant collectors for its unique floral form and botanical interest.

Risks & Threats
Although Strophanthus amboensis is not known to be naturalized in Hawaiʻi, it does possess traits that are cause for concern. Its vining growth habit could allow it to smother or outcompete nearby vegetation if it were to establish in suitable habitats, and its production of toxic compounds raises additional concerns for human, livestock, and wildlife exposure. Species in this genus may also produce wind-dispersed seeds that can aid in spread under favorable conditions. Given these characteristics, caution is recommended to ensure that S. amboensis does not negatively impact Hawaiʻi ecosystems. Ongoing evaluation is needed to better understand its potential behavior in island environments, particularly in wet or mesic forest systems where climbing vines can become disruptive if they naturalize.

High Risk Traits:

• Grows in tropical climates
  
• Seeds toxic to animals and people
  
• Tolerates many soil types
  
• Shrub or liana (and potentially capable of climbing and possibly smothering other vegetation)
  
• Reproduces by wind-dispersed seeds
  
• Gaps in biological and ecological information may reduce accuracy of risk prediction

Low Risk Traits:

• No reports of invasiveness or naturalization, but no evidence of widespread introduction outside native range
  
• Unarmed (no spines, thorns, or burrs)
  
• Grows in full sun, which may limit ability to spread into dense forest
  
• Not reported to spread vegetatively
  
• Slow growing when young, reaching maturity after 3+ years