Family: Apocynaceae
Origin, Description & Uses
Strophanthus gratus is a flowering vine native to West and West-Central Tropical Africa, where it grows in forested regions and woodland edges. It is known for its striking, showy flowers—often pale pink to white with a deep red or purple throat—and glossy green foliage. In its native range, it is sometimes cultivated as an ornamental for its dramatic blooms and climbing habit, and it has also been historically noted for compounds derived from its seeds that were used in traditional applications.
Risks & Threats
This species is not known to be naturalized in Hawaiʻi and is generally considered to have a low likelihood of becoming invasive under current conditions. It does not show strong traits associated with aggressive spread in island ecosystems. However, as with any non-native ornamental plant, continued observation is appropriate to ensure it does not escape cultivation or interact negatively with sensitive habitats over time. Native or Polynesian-introduced plants remain the preferred choice for supporting Hawaiʻi’s ecosystems.
High Risk Traits:
- Broad tropical native range
- History of repeated introductions outside its native range
- Climbing and smothering growth habit (liana)
- Contains cardiac glycosides (toxic to animals and humans)
- Produces viable seeds
- Seeds adapted for wind dispersal
- Seeds dispersed intentionally by people as an ornamental
- Congeneric (S. speciosus) listed as a weed
- Shade tolerant
Low Risk Traits:
- No evidence of naturalization or weediness outside native range
- Grows in a relatively narrow climate range (low elevation, moist tropical forests)
- Self-incompatible (requires cross-pollination, with potential specialist pollinators)
- No spines, thorns, or burrs
- Lacks traits for external animal dispersal (no hooks or barbs)
