Commonly known as “reriang” in Malay or Cicada tree, Ploiarium alternifolium is a shrub or small tree of the family Bonnetiaceae. This tree is found growing in terrestrial habitats from lowland including secondary rainforests, riverine, freshwater swamp forests, disturbed areas or open grounds, up to 1,300 m on mountain tops. The genus Ploiarium, is derived from the Greek word “ploion” meaning boat or canoe, which refers to the shape of the capsule valves. Meanwhile, the species epithet derives from two Latin words: “alternus” which means alternate and “folium” which means leaf, referring to the leaf arrangement (MyBIS, 2023).
Ploiarium alternifolium usually grows up to 10 m and rarely to 25 m tall, and the trunk diameter is 10-15 cm, depending on the locality. Plants growing in the river can grow only up to a height of 0.3 m, but those in swamps on peaty soil can reach up to 30 m. When grown in swamps, large numbers of thin stilt roots emerge from the trunk to help anchor the tree in the soil. These roots can grow on the trunk up to 2 m above ground (Nparks Flora Fauna, 2023).
The leaves are densely arranged in a spiral formation along the branches. They are alternate, simple, glabrous, 5–11.5 cm long and 1.3–4 cm wide, with scarcely visible veins that are pinnately arranged. The leaf margin is pink and slightly toothed. The star-shaped flowers (2.5–3 cm wide) have pink-tinged green sepals and pink-tipped white petals. The petals are approximately egg-shaped and curled slightly inwards along the margin. A flower possesses a green stigma that splits into 5 parts at the tip and has numerous yellow stamens. The fruits are oblong-ovoid, measuring 15-20 cm long and 10 mm in diameter, which split open like an umbrella, and the seeds are approximately 3.5 mm long (Nparks Flora Fauna, 2023).
This species is distributed from Thailand and Cambodia to Peninsular Malaysia, Sumatra and Borneo. It is widely planted as an ornamental plant for its attractive cherry-blossom-like flowers and is suitable for streetscapes, parks and gardens. According to the Malaysia Plant Red List (Yong et al., 2021), this tree is categorised as Least Concern (LC).
