Family: Fabaceae

Origin, Description & Uses
Senna alata (candle bush) is native to a wide region extending from southwestern Mexico through tropical America. It is a fast-growing shrub or small tree known for its striking upright spikes of bright yellow flowers that resemble candles, often blooming profusely in warm, wet climates. The plant has been widely introduced around the tropics as an ornamental species for its showy floral display and rapid growth. In some regions, it has also been used in traditional medicine, particularly for skin conditions, and occasionally as a natural hedge or landscape accent in tropical gardens.

Risks & Threats
In Hawaiʻi, Senna alata is now naturalized on Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island. It spreads readily in disturbed sites, roadsides, and moist lowland areas, where it can form dense stands that outcompete and displace native vegetation. The species produces abundant seed and can establish quickly, especially in wet tropical environments, increasing its potential to expand further into sensitive habitats. Because it is naturalized across multiple islands and possesses traits that are cause for concern, it could detrimentally impact tropical island ecosystems by reducing habitat quality and limiting native plant regeneration. Where suitable, low-risk or native alternatives are recommended for landscaping, and in areas where it is already established, efforts should focus on preventing further spread into uninfested natural areas to minimize additional ecological impacts.

High Risk Traits:

• Naturalized widely across the tropics
  
• Agricultural weed (noxious in Australia)
  
• Environmental weed (wetlands, high-water-table areas)
  
• Congeneric species are weedy
  
• Host for crop pathogens (fungi affecting beans, grapes, tomatoes, mango, etc.)
  
• Forms dense thickets
  
• Tolerates various soil types
  
• Viable seed production
  
• Regrows from root suckers
  
• Flowers in first year (rapid generation time)
  
• Likely persistent seed bank (hard-coated seeds)
  
• Resprouts after cutting
  
• Poorly controlled by herbicides

Low Risk Traits:

• No spines, thorns, or burrs
  
• Not allelopathic or parasitic
  
• Palatable to livestock
  
• Not toxic to animals or humans (medicinal use)
  
• Not shade-tolerant (prefers full sun)
  
• No vegetative spread
  
• No wind, water, bird, or external animal dispersal
  
• Seeds large – not likely to be contaminants or dispersed unintentionally
  
• Low seed output (not prolific)