Plant of the Week
Hairy-Fruited Hibiscus (Hibiscus lasiocarpos)
By Melissa Simpson, Forest Service Ecologist
Hibiscus lasiocarpos, known as the hairy- fruited hibiscus or rose-mallow, is a self-compatible herbaceous perennial native to fresh and brackish marshes of the southern and eastern United States. It is a member of Malvaceae, the same family as cotton, okra, and hollyhock. It can be found growing in full sun to partial shade along stream banks, lake edges, wet ditches, marshes, and flooded fields. The plant is easily distinguishable in the field because it is tall and has a large, showy flower.
Individual plants produce many shoots that grow 1-2 meters tall that emerge from a large, woody rootstock each spring. The plants are in bloom July through September and individual flowers are only open for a single day. Flowers are l0-15 cm in diameter and have 5 white or pale pink petals with a deep crimson center.
The reproductive structures of these flowers are found emerging from the center of the flower on a single stalk-like structure. The stamens are fused into a tube with numerous anthers that offer an abundance of pollen. The stalk ends with a branched style that supports 5 rounded stigmas. These flowers produce so much pollen that it often falls off the anthers and can be found resting in small piles on the lower petals.
A characteristic that distinguishes this plant from other Hibiscus within its range is its pubescent leaves and stems. The leaves are covered by soft, dense hairs on the upper and lower surfaces and are velvety to the touch. The degree of pubescence varies from flower to flower, but the velvety nature of the leaves can often be easily seen from a distance.
The fruit is a capsule that is densely-hairy and contains many seeds. The capsule opens to reveal the seeds and remains on the plant through much of the dormant season, making it easy to collect seeds to plant in your native garden!
This is an important flower to have in the ecosystem and also to plant in your native pollinator garden. It serves as a nectar source for butterflies and other insects and a pollen and nectar source for a variety of bee species. The specialist bee, Ptilothrix bombiformis, uses this plant as a primary pollen source to feed its larvae. These beautiful flowers are also a dating hot-spot, as male and female Ptilothrix will meet at the flowers to mate. The female bee collects the pollen grains and carries them in specialized hairs on her rear legs to transport them to her nest. She then sculpts the pollen into a ball, lays an egg on it, and seals the nest to allow the larvae to develop over the winter. This pollen mass provides the larvae with all the nutrition it needs to develop into an adult. The next summer, Hibiscus blooms again, the new adults emerge from their nest, and the harmony between flower and bee continues for another generation.