Morphology of Hibiscus Rosa-Sinensis

The Chinese or tropical hibiscus (Hibiscus rosa-sinensis) probably no longer exists in the wild, but only as a genetic line of ornamental plants in gardens. Believed native to southernmost China, this plant produced flowers with blood red petals. Modern tropical hibiscus hybrids display a wider array of color because of centuries of breeding and selection for different petal colors, ornateness and shapes. The basic morphology of all tropical hibiscus plants retains the main features of the original Asian plants.

Tropical hibiscus is a woody plant, often described as being either a small tree or large shrub. A mature plant usually develops a rounded shape, with an oval, upright habit. It matures 5 to 15 feet tall. With hundreds of extant cultivars, the mature tropical hibiscus can grow with a densely branched, rounded silhouette or with a low, mounded but spreading shape with fewer branches--all dependent on the cultivar. The bark is grayish brown to gray and becomes almost corky on large, old plants.

The evergreen foliage on tropical hibiscus plants resembles pointed ovals. The leaf blade is a wide, tapering oval with a pointed tip. The base of the leaf, where it attaches to the petiole stem, is either rounded or wedge-shaped. Leaf edges lack any imperfections, or more commonly, sparse, short teeth. Tropical hibiscus leaves never display lobes. Each leaf measures, on average, 3 to 4 inches long and 2 to 3 inches wide.

If temperatures are warm and soil moisture is adequate, tropical hibiscus blooms year-round. Flower buds arise from the branch tips anywhere on the plant. Several flowers may be produced on each branch tip, but only one at a time. Each bud opens into five green sepals under five papery petals. Each petal is oval, and depending on the cultivar, overlaps onto the next or just touches it. In the center of the wide-opening, funnel-shaped bloom is a long staminate column about 2 to 4 inches long. At the outer reaches of the column are numerous horizontal anthers that shed pollen. At the very tip is a five-branched style of the female sex organ.

Pollination of the style's five branches leads to seed production in a rounded green capsule fruit. The flower petals wither and fall away, but the green sepals remain and partially hide the swelling capsule, sometimes just referred to as a seed pod. When ripe, the pod is 1 inch long and dries to a light brown. The fruit naturally splits open to release up to 60 seeds--but usually 10 to 20--that are dark brown and roughly the size of apple seeds.