Family: Bignoniaceae
Origin, Description & Uses
Markhamia zanzibarica, commonly known as bell bean tree or maroon bell bean, is a fast-growing flowering tree native to eastern and southern Africa, ranging from southern Somalia to northeastern Namibia. It is valued as an ornamental for its attractive clusters of trumpet-shaped flowers, glossy foliage, and upright form. The flowers are typically reddish to maroon with yellow markings and attract pollinators such as bees and birds. This species is planted in tropical and subtropical landscapes as a shade tree, specimen tree, or street tree, and is appreciated for its drought tolerance and showy appearance. In Hawai‘i, it has become naturalized on O‘ahu.
Risks & Threats
Although Markhamia zanzibarica is considered a low-risk species, its ability to naturalize in Hawai‘i shows that it can reproduce and persist outside cultivation. At present, there is little evidence that it spreads aggressively or causes significant ecological harm. However, as with many introduced ornamental trees, seedlings may occasionally establish in disturbed areas, roadsides, or unmanaged landscapes. Monitoring naturalized populations and preventing unwanted spread into sensitive habitats is recommended. When planting, gardeners can help minimize potential impacts by managing seedlings and avoiding planting near native forests or conservation areas.
High Risk Traits:
- Naturalized on O'ahu
- Grows and could potentially spread in tropical climates
- Reproduces by seeds
- Seeds dispersed by wind, possibly water, and intentionally by people
- Able to coppice and resprout after cutting
- Gaps in biological and ecological information may reduce accuracy of risk prediction
Low Risk Traits:
- No reports of invasiveness, but no evidence of widespread introduction outside native range
- Unarmed (no spines, thorns, or burrs)
- Provides fodder for livestock
- Non-toxic
- Grows in full sun (and spread into dense, shaded forest may be prevented)
- Not reported to spread vegetatively
