Family: Apocynaceae

Origin, Description & Uses
Cascabela (Cascabela thevetia), also known as be-still tree, yellow oleander, or lucky nut, is a small evergreen tree or large shrub native to Mexico, Central America, and tropical South America. It is prized as an ornamental for its bright yellow, funnel-shaped flowers, glossy narrow leaves, and tolerance of heat, drought, and poor soils. The species is commonly planted in tropical and subtropical landscapes as a hedge, specimen plant, or along roadsides, where its long flowering season and low maintenance requirements make it attractive. Despite its beauty, all parts of the plant are highly poisonous if ingested.

Risks & Threats
Be-still tree is naturalized in Hawaiʻi and possesses traits that are cause for concern. It produces abundant seeds that are readily dispersed by water and human activities, allowing it to spread beyond cultivation into disturbed sites, coastal habitats, roadsides, and dry forests. Once established, it can form persistent populations that compete with native vegetation and contribute to the degradation of tropical island ecosystems. Because this species is already widespread on several Hawaiian Islands, further planting should be avoided, and existing plants should be carefully managed to prevent additional spread into areas where it is not yet widely established. Whenever possible, choose a low-risk or native alternative for landscaping to help protect Hawaiʻi’s unique natural environments.

High Risk Traits:

• Naturalized in Hawaii, Puerto Rico, and multiple Pacific islands
  
• Naturalized on multiple Hawaiian Islands (Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui) and at Kuaihelani (Midway Atoll)
  
• Agricultural weed (Papua New Guinea) and dryland weed (Australia)
  
• Category 1 environmental invader in South Africa
  
• Highly toxic to livestock and humans (seeds lethal if ingested)
  
• Host for Queensland and Mediterranean fruit flies
  
• Widely planted as ornamental; intentionally dispersed by people
  
• Bird-dispersed seeds with gut survival
  
• Tolerates a wide range of soils
  
• Repeated introductions outside native range

Low Risk Traits:

• No spines, thorns, or burrs
  
• Used as forage in some systems (despite toxicity)
  
• Fire-resistant; requires full sun (not shade-tolerant)
  
• No vegetative reproduction; reproduces by seed only
  
• Bird-pollinated (specialist pollinators)
  
• No wind, water, or external animal dispersal (seeds too large)