Family: Moraceae
The Panama rubber tree, Castilla elastica, is a tropical tree native to regions from southern Mexico to northern South America. Historically, it was an important source of natural rubber before the commercial dominance of the Brazilian rubber tree. Today, it is valued for its ornamental and landscaping use in tropical climates, where it grows quickly and has a broad, attractive canopy.
However, this tree carries significant ecological risks outside its native range. It is a high-risk invasive species that has damaged rainforests in places like American Samoa and is considered a threat in other tropical locations. Its ability to produce many seeds, which are spread by birds and mammals, allows it to readily invade and compete with native plants, altering natural habitats.
High Risk Traits:
- Naturalized in Samoa, Puerto Rico, Australia, Tanzania, French Polynesia, Singapore
- Thrives in tropical climates
- Environmental weed in American Samoa, invading intact rainforest and competing with native plants. Regarded as a potential environmental weed in other locations.
- Tolerates many soil conditions
- Self-compatible
- Seeds are bird and mammal dispersed
- Prolific seed production
Low Risk Traits:
- May be limited to lower elevations
- Unarmed (no spines, thorns or burrs)
- Non-toxic
- Prefers full sun and more open habitats
- May require thrips for pollination
- Landscaping and ornamental value
- Reaches reproductive maturity in >4 years
- No evidence of vegetative spread
