Alstonia scholaris (Chatim):

An In-Depth Botanical and Ecological Study

Alstonia scholaris, commonly known as Chatim, Devil Tree, or Blackboard Tree, is a tall evergreen species widely recognized for its ecological importance, medicinal value, and cultural significance across South and Southeast Asia. Belonging to the Apocynaceae family, this tree is notable for its straight trunk, whorled leaves, fragrant flowers, and latex-producing tissues. In forested landscapes, especially in moist tropical regions, Alstonia scholaris contributes significantly to canopy structure, microclimatic regulation, and habitat stability.

This article presents a thoroughly researched and scientifically structured overview of Alstonia scholaris, covering its taxonomy, morphology, habitat preferences, geographical distribution, ecological role, occurrence in the Sundarbans region, conservation aspects, and lesser-known facts. The intent is to offer a reliable and descriptive reference suitable for ecological documentation, academic study, and nature-based awareness initiatives.

Taxonomy & Classification

Systematic Position

Alstonia scholaris is a member of the Apocynaceae family, a diverse group known for latex-bearing plants and complex secondary metabolites. The genus Alstonia comprises several species distributed mainly in tropical regions, many of which are valued for medicinal or timber purposes.

• Kingdom: Plantae
• Clade: Angiosperms
• Clade: Eudicots
• Clade: Asterids
• Order: Gentianales
• Family: Apocynaceae
• Genus: Alstonia
• Species: Alstonia scholaris

The species name scholaris originates from the historical use of its wood for making slates or boards used by students, hence the common name “Blackboard Tree.”

Morphology & Field Identification

General Growth Form

Alstonia scholaris is a large, fast-growing evergreen tree that can attain heights of 30–40 meters under favorable conditions. The trunk is typically straight and cylindrical, with greyish to pale brown bark that becomes slightly fissured with age. When injured, the bark exudes a milky white latex, a characteristic feature of the Apocynaceae family.

Leaves

Leaves are arranged in distinctive whorls, usually in groups of four to seven at each node. They are simple, leathery, and obovate to elliptic in shape, with entire margins and a glossy dark-green upper surface. The prominent lateral veins run nearly parallel, giving the leaf a diagnostic appearance useful for field identification.

Flowers and Fruits

The flowers are small, greenish-white, and highly fragrant, often blooming in clusters during late summer to early autumn. Despite their modest appearance, the strong scent attracts a variety of nocturnal pollinators. The fruit consists of paired slender follicles containing numerous seeds, each equipped with tufts of silky hairs that facilitate wind dispersal.

Habitat & Distribution

Natural Habitat

Alstonia scholaris thrives in moist tropical and subtropical forests, commonly occurring in mixed evergreen and semi-evergreen forest types. It prefers regions with high annual rainfall, warm temperatures, and well-drained soils but demonstrates considerable ecological plasticity.

The species is frequently found along forest edges, riverbanks, and lowland plains, where light availability and soil moisture are adequate for rapid growth.

Global Range

The global distribution of Alstonia scholaris extends across South Asia, Southeast Asia, southern China, and parts of northern Australia. It is widely cultivated beyond its native range as an ornamental and shade tree due to its symmetrical crown and fragrant flowers.

In many regions, the species has become naturalized, particularly in urban and semi-urban landscapes, demonstrating its adaptability to varied environmental conditions.

Preferred Habitat

Climatic and Soil Preferences

The optimal habitat for Alstonia scholaris includes warm, humid climates with annual rainfall exceeding 1,500 mm. The species prefers deep, loamy soils rich in organic matter, although it can tolerate sandy and lateritic substrates when sufficient moisture is available.

Its tolerance to moderate drought and temporary waterlogging allows it to persist in transitional zones between upland forests and low-lying floodplains.

Occurrence

Alstonia scholaris occurs both as a naturally regenerating forest species and as a planted tree in rural and urban settings. In natural forests, it is often scattered rather than forming dense stands, contributing to structural diversity within the canopy.

In human-modified landscapes, the tree is commonly planted along roadsides, in institutional campuses, and around villages, where it provides shade and improves microclimatic conditions.

Preferred Habitat in the Sundarbans Region

Ecological Niche in the Sundarbans

Within the Sundarbans region, Alstonia scholaris is primarily found in slightly elevated areas and transitional forest zones where salinity levels are lower compared to core mangrove habitats. These zones often include embankments, village fringes, and mixed woodland patches adjacent to tidal forests.

The species benefits from the region’s high humidity and fertile alluvial soils, although its presence is limited in areas subjected to prolonged saline inundation.

Association with Other Flora

In the Sundarbans landscape, Chatim often grows alongside other non-mangrove and mangrove-associated species, forming ecotonal vegetation belts that enhance overall biodiversity and act as buffers against cyclonic winds.

Ecological Role

Canopy Structure and Microclimate Regulation

As a tall evergreen tree, Alstonia scholaris contributes to canopy formation and plays a role in regulating temperature and humidity beneath its crown. This creates favorable conditions for understory plants, epiphytes, and associated fauna.

Faunal Interactions

The fragrant flowers attract insects, particularly moths, which serve as pollinators. Birds and small mammals may use the tree for nesting or shelter, while the wind-dispersed seeds facilitate natural regeneration across open spaces.

Soil and Nutrient Dynamics

Leaf litter from Alstonia scholaris decomposes relatively quickly, contributing organic matter to the soil and enhancing nutrient availability. This process supports soil microbial communities and overall forest productivity.

Habitat Alteration

Anthropogenic Impacts

Deforestation, urban expansion, and infrastructure development have led to localized declines in natural populations of Alstonia scholaris. Removal of mature trees reduces seed sources and disrupts ecological continuity.

In coastal regions, increasing soil salinity due to sea-level rise and altered hydrology poses additional challenges to regeneration.

Climate-Related Stress

Extreme weather events such as cyclones and prolonged droughts can damage standing trees and affect flowering and seed production. While the species shows moderate resilience, repeated disturbances may limit long-term population stability.

Conservation Efforts

In-Situ Conservation

Protecting mixed forest patches and transitional woodlands is essential for conserving Alstonia scholaris in its natural habitat. Inclusion of the species in afforestation and coastal shelterbelt programs can enhance ecosystem resilience.

Awareness and Sustainable Use

Promoting awareness about the ecological and medicinal value of Chatim encourages sustainable management practices. Controlled use of its bark and latex, combined with regeneration initiatives, can help balance utilization and conservation.

Did You Know?

• Alstonia scholaris emits a strong fragrance at night, which is more intense than during the daytime.
• The tree produces milky latex that has been traditionally used in various herbal preparations.
• Its lightweight wood was historically used to make writing boards for students, giving rise to the name “Blackboard Tree.”
• The species can tolerate moderate air pollution, making it suitable for urban planting.

External Reference

Additional botanical and taxonomic details can be found on the Wikipedia page for
Alstonia scholaris.