In Hawai`i the native Lobelia species are woody which is unusual for this genus in which most of the species are herbaceous. In Lobelia niihauensis the stems are prostrate, meaning they sprawl over the soil surface, and can be up to 20-40 cm long with the branches limited to the lower half of the stem. The leaves are clustered at the tips of the branches and are alternately arranged along the stem. They are 7-15 cm long and 0.7-1.8 cm wide and the margins are finely toothed with serrations that have rounded tips. The inflorescences (clusters of flowers) of the Hawaiian Lobelia species are beautiful and very distinctive. They develop from floral buds at the tips of the branches and may contain up to 200 flowers in some Lobelia species. In Lobelia niihauensis the inflorescences are 12-15 cm long and produce many magenta flowers. The calyx (sepals) and corolla (petals) of Lobelia flowers are fused at the base forming a structure called a hypanthium. This structure surrounds the ovary in which the seeds are borne following fertilization. The petals in Lobelia niihauensis flowers are fused partway along their length but are distinct at their tips. As the flowers mature the petal lobes spread open and eventually roll back to expose the stamens and the stigma in the flower. The fruit of Lobelia is a capsule that is 6-8 mm long and is dry at maturity. Two valves are present at the tip of the fruit that open when the fruit is mature to release the seeds. Many small, brown seeds that are 0.5 mm long and smooth are produced in the fruit. (Wagner, W. L., Herbst, D. R., and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i. Revised Edition. Volume 2. Bishop Museum Special Publication 97. University of Hawai`i Press, Bishop Museum Press, Honolulu, Hawai`i.)
Lobelia niihauensis is currently found on the eastern Wai`anae Mountains, O`ahu and Kaua`i. As the name suggests it is known to have been present in Ni`ihau however, no plants are currently known from there, and collections from Ni`ihau are known only from herbarium specimens. This species grows on exposed dry to mesic cliffs from 125-725 m. The genus Lobelia contains around 350 species and has a cosmopolitan distribution meaning that it is found throughout the world. There are thirteen endemic Lobelia species in Hawai`i. The Hawaiian species may represent two independent colonization events as the species with blue or magenta flowers (including L. niihauensis) are thought to be closely related to tropical Asian species and those with crimson, yellow, or greenish white flowers are thought to be more closely related to Brazilian or eastern Asian species. (Endangered and Threatened Wildlife and Plants; Revised Determinations of Prudency and Proposed Designations of Critical Habitat for Plant Species From the Islands of Kauai and Niihau, Hawaii. Federal Register Volume 67 (18): 4089-4098) (Wagner, W. L., Herbst, D. R., and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i. Revised Edition. Volume 1. Bishop Museum Special Publication 97. University of Hawai`i Press, Bishop Museum Press, Honolulu, Hawai`i.)
Lobelia niihauensis is designated as an endangered species under the United States endangered species act. A recovery plan was established in 1995 and updated in 1998 and current estimates are that 0-25% of those recovery objectives have been reached. As a woody, perennial species the aim of restoration efforts for Lobelia niihauensis is to maintain 5-10 populations on each of the islands, on which it is found, with each population containing 100 individuals. The number and size of Lobelia niihauensis populations are estimates only and further survey work is necessary to accurately assess population number and size.
We currently have 30 herbarium specimens for Lobelia niihauensis in our collection. Click on any specimen below to view the herbarium sheet data.
