Differences Between Plumeria and Hibiscus

Flower Size

• Tropical hibiscus, grown in USDA zones 9 through 11, produces smaller 4- to 8-inch-wide blossoms compared to their hardy relatives' 6 inch to 10 inch flowers. One of the main reasons for the blossom size difference is the surrounding environment. Heat stress causes tropical hibiscus to direct energy into foliage and root activity -- both parts actively conserve water as they absorb it into their vascular system. Plumeria's warm weather preference also makes it generate subtle blossoms ranging between 2 inches and 4 inches wide. Any unseasonable cold snaps may damage blossoms on both plumeria and tropical hibiscus, but hardy hibiscus cultivars easily thrive in mild temperatures.

Reproductive Organs

• Hibiscus displays its long stamen and style configuration prominently at the center of colorful flowers; these reproductive organs produce pollen for flower fertilization and seed development. In contrast, plumeria strategically form their reproductive organs deeply within each blossoms' center point. Only tiny insects, like thrips, can move into the plumeria to jostle the pollen grains for self-pollination. Hibiscus relies on butterflies and hummingbirds for pollen transfer; these pollinators travel between flowers with pollen grains attached to their bodies for a diverse pollination strategy.

Plant Appearance

• Plumeria plants are technically small trees that can be either deciduous or evergreen, based on the variety and surrounding environment. Growing as tall as 30 feet, periodic pruning encourages more limbs to grow as new flowers emerge from the young shoots. Hibiscus remains an evergreen shrub that may grow to a 15 foot height, depending on the cultivar. These bushes also benefit from pruning to generate more prolific blossoms in the spring.

Fragrance

• Growing individually or in small groups, hibiscus flowers use their visually stunning petals to attract pollinators -- they do not have fragrance. Known for their use in Hawaiian leis, plumeria produces an intoxicating scent to entice pollinators. Their subtle flower size and color may not attract pollinators as quickly as larger flowers nearby. They use their scent as a powerful attractant while blossoms grow in dense clusters on outstretched tree limbs. Both plumeria and hibiscus flowers are short-lived, but they continue to flower consistently between spring and fall.