Family: Anacardiaceae

Origin, Description & Uses
Semecarpus anacardium, commonly known as marking nut tree, is a medium-sized deciduous tree native to the Indian Subcontinent and Myanmar. It is characterized by its broad, leathery leaves, small greenish-white flowers, and distinctive black fruits that contain a caustic resin. The species has a long history of use in traditional Ayurvedic medicine, where extracts from the nuts and other plant parts have been used for various medicinal purposes after careful processing. It is also occasionally cultivated as an ornamental or specialty tree in tropical and subtropical regions.

Risks & Threats
Although Semecarpus anacardium is not known to be naturalized in Hawaiʻi, it possesses traits that are cause for concern. The species produces abundant fruits that may be dispersed by animals, potentially allowing it to spread beyond cultivation in suitable climates. In addition, the plant contains highly irritating compounds that can cause severe skin reactions in humans and animals, creating potential health and management concerns. Because Hawaiʻi’s climate is similar to portions of the tree’s native range, ongoing evaluation is needed to determine whether it could establish and impact local ecosystems. Caution is recommended when cultivating this species to ensure that it does not negatively affect Hawaiʻi’s environment.

High Risk Traits:

• Broad tropical/subtropical climate tolerance (0–1000 m, 21–36°C)
  
• Already naturalized or cultivated across Asia, Australia, and Africa
  
• History of repeated human introductions outside native range
  
• Sap toxic and corrosive to animals and humans (causes blisters)
  
• Shade tolerant and grows on a wide range of soils
  
• Self-compatible (can self-pollinate)
  
• Actively dispersed intentionally by humans for nuts, oil, medicine, and ink
  
• Seeds dispersed by birds and mammals; survive gut passage
  
• Coppices readily and resists fire

Low Risk Traits:

• No evidence of naturalization or weediness anywhere
  
• No spines, thorns, or allelopathic effects
  
• No vegetative spread (reproduces only by seed)
  
• Large seeds (2.5–3.8 cm) — not wind-, water-, or contaminant-dispersed
  
• Not a prolific seed producer
  
• Short seed bank viability (<1 year)