The plant genus Hymenosporum belongs to the Pittosporaceae family and has only one species — Hymenosporum flavum. Growers cherish it for its lovely flowers, which grow in umbel, or umbrella-shaped, panicles or terminal corymbs. The flowers end in tubular shapes with five oblong lobes. Often these lobes twist and curl as they open, giving the flowers an interesting appearance. In its native New Guinea and eastern Australia habitats, it is an evergreen shrub or tree.
Commonly known as the Australian frangipani, Hawaiian wedding tree, or sweetshade, this semi-tropical plant may be a large shrub or small tree, depending on its environment or cultivator. The height may vary between approximately 12 to 70 feet (4 to 20 m), with a spread of 10 to 20 feet (about 3 to 6 m). The plant usually has one main trunk with well-spaced, bushy branches. It sports glossy, dark green leaves that are lighter green on the underside. Generally the leaves are lance- or obovate-shaped and about 2.5 to 6 inches (6 to 15 cm) long.
In addition to being an attractive shrub or tree, the Hymenosporum flavum often produces masses of fragrant, trumpet-like flowers that grow in loose, often drooping, panicles that may measure up to 8 inches (about 20 cm) across. Each flower is approximately 1 to 1.25 inches (about 2.5 to 3 cm) across. Their color progresses from creamy white to deep yellow or orangish yellow as they age. Sometimes the flowers have red centers, varying in size from a small spot to heavy blushing on the flower petals. Frequently, several stages of blooms are on each panicle at the same time, giving the tree a range of bloom colors.
As a rainforest plant, Hymenosporum flavum generally is not frost tolerant. In the U.S., it is listed as zones nine to 10 on the USDA hardiness scale, which lists minimum temperatures as 20°F to 30°F (about -7°C to -1°C). Often landscapers plant these trees in industrial or commercial areas in southern California. Gardeners generally raise them as specimen plants. Shrubby plants planted in a garden or landscape often tolerate light or dappled shade.
Gardeners may propagate the plants by sowing the seeds in the spring. Another method is rooting stem cuttings, which growers generally do during the hot summer months. The plants also usually respond well to air layering, especially in the cooler climates of the spring or autumn. Typically, most gardeners buy them as nursery stock.
Each light brown seedpod contains many seeds, each enclosed in a small, papery, round envelope. The name Hymenosporum is derived from Greek words. Hymen is Greek for membrane, and spora means seed. Together, they refer to these winged seeds.