Family: Apocynaceae

Alstonia scholaris, commonly known as the scholar tree or blackboard tree, is a large evergreen tree native to tropical and subtropical regions of Asia and northern Australia. This species is characterized by its tall stature, reaching up to 40 meters, and its distinctive whorled leaves and white, fragrant flowers. The tree produces a milky latex and has a corky grey to grey-white bark. Its timber, known as pulai, is lightweight and has been traditionally used for making blackboards, which is reflected in its species name “scholaris.” In traditional medicine, various parts of the tree, including the bark and leaves, contain alkaloids such as echitamine and ditamine, which have been used for their medicinal properties, including as anthelmintic and antidiarrheal agents.

Despite its beneficial uses, Alstonia scholaris is considered toxic and should be handled with care. The plant contains alkaloids that can cause adverse effects if consumed in large quantities, including damage to major organs in both rats and mice. The toxicity varies depending on the plant organ and the season it is harvested, with bark collected in the summer being more toxic than that collected in the monsoon season. Additionally, the tree’s rapid growth and large size can lead to structural issues in urban environments, such as sidewalk damage and susceptibility to wind damage. In some regions, its strong fragrance during flowering has been noted to cause allergic reactions in sensitive individuals.

High Risk Traits:

• High climate match for tropical/subtropical regions.
  
• History of repeated introductions outside its native range.
  
• Naturalized in non-native areas (e.g., Florida, USA).
  
• Toxic to animals.
  
• Tolerates a wide range of soil types and conditions.
  
• Intentionally dispersed by humans for ornamental use.
  
• Seeds are wind-dispersed, facilitating long-distance spread.
  
• Resprouts after damage (coppices and produces root suckers).

Low Risk Traits:

• No physical defenses like spines or thorns.
  
• Not allelopathic, parasitic, or a major host for economic pests.
  
• Does not create a fire hazard or form dense thickets.
  
• Seeds are not dispersed by water, birds, or as a contaminant.
  
• Short-lived seed bank (seeds remain viable for only ~2 months).