Hoya coronaria Blume gets its species name from the Latin word “coronaria” meaning crown because of the resemblance of its flower to a crown. The name “Hoya” honors Thomas Hoy, a gardener to the Duke of Northumberland, who brought this plant into prominence. The species was first described by the German botanist, Carl Ludwig Blume. The common name for Hoya is wax flower and locally it is known in Malay as akar setebal which refers to its thick stem (Lemmens & Bunyapraphatsara, 2003). Hoya coronaria is among approximately 550 species of Hoya that belong to the Apocynaceae family (formerly included in Asclepiadaceae) that have latex. It falls into Section Eriostemma with the distinctive feature in most of them having stems and leaves with soft hairs, large flowers, and a thick hirsute calyx.
This climbing plant can reach up to 5 meters in length (Sri Rahayu, 2006). Hoya coronaria leaves are thick, light green, elliptic, up to 14 x 7.5 cm in size and velvety. It has bisexual flowers and is easily recognized by the unique form of its inflorescence that grows in an umbel shape with small star-shaped calyx (Ridley, 1923). The colour of the corolla varies from whitish, reddish, brownish to yellowish. The texture of the thick corolla is waxy. Some people with hypersensitive skin may experience skin irritation from contact with the hairs and latex of this species. The latex is white in colour and poisonous. Its pale coloured flowers and production of a strong scent at night suggests that it is pollinated by moths (Rintz, 1978). This species grows in mangrove swamps and lowland forest on various soil types and is widely distributed in Peninsular Thailand, throughout the Malesian region, the Solomon Islands and northern Australia (Lemmens & Bunyapraphatsara, 2003). Since it is common, it is not considered threatened.
The attractive corolla of Hoya make them popular as exotic ornamental plants in the USA and Europe (Ritz, 1978). Hoya can be cultivated through propagation of parts of the stem, leaf and seeds. In nature, H. coronaria often occurs rooted in loose and highly organic soil. Trimming is required if the plant becomes too compact. Pruning at old blossom spurs should be avoided as a new inflorescence will grow from the same spot (Sri Rahayu, 1994). Hoya needs semi-shade conditions as too much exposure to sunlight will turn the leaves yellow. Hoya can bloom a maximum of once a month and usually blooms less frequently, remaining dormant for months in between inflorescences (Ritz, 1978).
