About Hymenosporum flavum (Hook.) F.Muell.
Hymenosporum flavum (Hook.) F.Muell. is a semi-deciduous tree that reaches up to 25 m (82 ft) in height, with a trunk diameter at breast height (DBH) of up to 45 cm (18 in). Its leaves are simple, obovate, and arranged alternately; they are glossy green on the upper surface and lighter on the lower surface. The leaves grow up to 13 cm (5.1 in) long by 4.5 cm (1.8 in) wide, and are clustered near the ends of branches in pseudo-whorls.
The flowers of this species are very fragrant, quite large, and measure around 40 mm (1.6 in) in diameter, with a floral tube up to 28 mm (1.1 in) long. When flowers first open, they are functionally male, and colored white with faint lemon tinges. Over approximately 5 days, the stigma develops and the stamens curl inward. At the same time, the flower’s color deepens; when the flower becomes fully functionally female, it is golden yellow with red or purple track lines in the throat.
The fruit is a dehiscent two-chambered capsule, black to brown in color, densely hairy, and about 35 mm (1.4 in) both wide and long. The numerous seeds are around 7 mm (0.28 in) long with a 4 mm (0.16 in) wing, and are stacked together to fill each capsule chamber.
The native range of Hymenosporum flavum extends from New Guinea south through coastal Queensland to northeastern New South Wales. It grows in rainforest or wet sclerophyll forest on a variety of soil types. Flowering occurs from early spring to early summer, and fruits ripen around May.
Commonly called native frangipani, this species is widely cultivated. Cultivated specimens usually grow to around 8 meters in height, though wild individuals in rainforest can reach over 20 meters tall. It can be grown in shaded locations, but produces the most flowers when grown in full sun. In Australia, it is commonly planted along suburban streets, shopping boulevards, and walkways between tall buildings. It prefers well-drained soil with high organic content, but is highly adaptable to other conditions. Very young seedlings are easily killed by frost, but if they are kept in a sheltered position until they reach 1–1.5 meters in height, they will grow well in cooler areas, as long as they have access to water during hot, dry periods. Hymenosporum flavum is included on the Tasmanian Fire Service's list of low flammability plants, meaning it is suitable for planting within a building protection zone.
