Family: Boraginaceae

Origin, Description & Uses:
Heliotropium arboreum (tree heliotrope) is a coastal shrub or small tree native to a vast range of tropical and subtropical shorelines across the Indo-Pacific and parts of the Indian Ocean, from East Africa and islands such as Madagascar and Seychelles through Southeast Asia, Australia, and across the Pacific Islands. Well adapted to harsh coastal conditions, it thrives in sandy, saline soils and areas exposed to strong winds and salt spray. The plant forms dense stands of silvery-green foliage and produces clusters of small, white, fragrant flowers year-round. It has been widely used for erosion control, windbreaks, and ornamental coastal landscaping. In Hawaiʻi, tree heliotrope is now naturalized on many islands and atolls, including Mokupāpapa (Kure Atoll), Kuaihelani (Midway Atoll), Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, and Maui.

Risks & Threats:
Tree heliotrope is naturalized in Hawaiʻi and possesses traits that are cause for concern, including rapid growth, high seed production, and the ability to form dense thickets that can displace native coastal vegetation and alter sensitive shoreline ecosystems. These impacts may reduce habitat availability for native species and contribute to long-term ecological change. However, with the widespread loss of native coastal plant communities, tree heliotrope now plays an important ecological role in some areas. It provides a critical floral resource for Hylaeus anthracinus, an endangered native yellow-faced bee. Despite this benefit, its potential to spread and dominate coastal habitats warrants careful management, and the use of low-risk or native alternatives is recommended whenever feasible.

High Risk Traits:

• Naturalized in tropics/subtropics (e.g., Hawaii)
  
• Congeneric weeds exist
  
• Tolerates poor, sandy, or limestone soils
  
• Viable seeds produced
  
• Seeds dispersed by water (buoyant) and birds
  
• Seeds survive gut passage
  
• Prolific seed production (>1000/m²)
  
• Persistent seed bank (>1 year)

Low Risk Traits:

• Palatable to livestock (used as pig food)
  
• Non-toxic to animals and humans (leaves edible)
  
• Not shade tolerant
  
• A critical floral resource of the endangered Yellow-faced bee (Hylaeus anthracinus)
  
• No external dispersal mechanisms (no hooks/barbs)
  
• Slow to mature (4+ years to reproduce)