Alstonia scholaris

Alstonia scholaris, known widely as the Blackboard Tree or Devil's Tree, is one of the more recognizable evergreen trees across South and Southeast Asia. Belonging to the family Apocynaceae, it grows in tropical forests, along roadsides, and within temple grounds throughout Sri Lanka, where it is catalogued as part of the country's official Ayurvedic medicinal plant heritage. Its tall, straight form, striking whorled leaves, and strongly scented white flowers make it easy to identify once you know what to look for.

What does Alstonia scholaris look like?

Mature specimens typically reach between 30 and 40 metres in height, with a trunk that remains notably straight and cylindrical. The bark is grey-brown, often marked with horizontal lenticels, and exudes a milky white latex when cut — a characteristic shared across the Apocynaceae family. Leaves are arranged in neat whorls of four to seven around each node, dark green and glossy on the upper surface. From around October to February, the tree produces clusters of small, pale greenish-white flowers with a powerful, almost medicinal fragrance that carries well at night, attracting moths and other nocturnal pollinators.

The fruit consists of pairs of long, slender pods that eventually split to release seeds equipped with tufts of hair, allowing wind dispersal across considerable distances.

Where does Alstonia scholaris grow in Sri Lanka?

The tree is found across the lowland wet and intermediate zones of Sri Lanka, from sea level up to around 1,000 metres. It grows naturally in secondary forests and along waterways, and has been widely planted in gardens, school grounds, and the precincts of Buddhist and Hindu temples. Urban specimens are common in Colombo and Kandy, where the tree's canopy and tolerance of roadside conditions make it practical for avenue planting. In rural areas, older trees sometimes mark the boundaries of village common land, where they have stood for generations.

What are the medicinal uses of Alstonia scholaris?

The tree occupies a well-established place in Ayurveda, Siddha, and Unani systems of medicine, primarily through preparations made from the bark. Traditional practitioners use the bark to address respiratory complaints — including chronic bronchitis and asthma — as well as intermittent fevers and certain digestive disorders. The latex has historically been applied topically to wounds, rheumatic joints, and skin infections.

Phytochemical studies have identified a range of alkaloids in the bark and leaves, including ditamine, echitamine, and scholaricine. Research published in peer-reviewed journals points to anti-inflammatory, antimicrobial, and antimalarial activity associated with these compounds, lending scientific support to longstanding traditional use. It is worth noting that self-medication with any plant-derived compound carries risks; medicinal use should be guided by qualified practitioners of Ayurveda or conventional medicine.

• Bark: preparations used for fever, malaria, and respiratory conditions in traditional medicine
• Leaves: poultices and decoctions used in some regional traditions for skin complaints
• Latex: applied topically in folk medicine for joint pain and wounds
• Alkaloids: echitamine and related compounds are subjects of ongoing pharmacological research

What is the ecological role of Alstonia scholaris?

The tree's dense canopy provides reliable shade and nesting sites for a variety of bird species, while the strongly scented flowers draw pollinators — particularly moths — that are active after dark. The long, hair-bearing seeds rely on wind for dispersal, allowing the species to colonise disturbed ground and secondary forest edges relatively quickly. Root systems contribute to slope stabilisation in hilly terrain, and the tree's tolerance of degraded soils means it often appears as an early-returning species in areas recovering from agricultural use.

In garden and urban settings, the tree's ability to filter particulate matter from the air has made it a recommended species in some South and Southeast Asian urban greening programmes. Its evergreen habit means the canopy remains intact year-round, offering consistent habitat value.

Why is the Blackboard Tree culturally significant?

The common name 'Blackboard Tree' is said to derive from the historical use of the tree's lightweight, even-grained timber to make writing slates and school boards, though this etymology is debated. More consistently documented is the tree's association with places of learning and worship: it is planted near temples and schools across Sri Lanka, India, and parts of Southeast Asia, carrying a symbolic connection to knowledge, protection, and continuity.

In Sri Lanka, older Alstonia trees near temples and rural shrines are sometimes treated as sacred, with small offerings placed at their base. The fragrance of the flowers, particularly strong in the cooler night air, is closely associated in local memory with the atmosphere of religious festivals held in the months around the flowering season.

The tree is formally recognised in Sri Lanka's catalogue of Ayurvedic medicinal plants, a government classification that supports its cultivation and conservation within the country's traditional medicine sector.

How is Alstonia scholaris used in timber and crafts?

The wood of Alstonia scholaris is soft, light, and white to cream in colour. It seasons well with minimal warping and was traditionally worked into pencils, packing cases, and small carved items. In parts of South Asia, it has also been used for making matches and cork substitutes. The wood is not regarded as durable for outdoor structural use but remains valued for interior applications where its lightness and workability matter more than strength.

Is Alstonia scholaris a protected or threatened species?

The species is currently listed as of least concern on the IUCN Red List, reflecting its wide distribution and adaptability across a range of tropical habitats. In Sri Lanka, wild populations are not considered under immediate threat, and the tree is actively cultivated in government Ayurvedic gardens and private nurseries. Nonetheless, the conversion of lowland wet-zone forest — the tree's primary natural habitat in Sri Lanka — remains a long-term pressure on many forest-associated species in the region.