Trematolobelia grandiflora of Kohala Mountain, Hawaii

Trematolobelia is an enigmatic genus, perhaps most closely related to the genus Lobelia, particularly its section Galeatella. Various classification schemes through the years have identified the genus as Trematocarpus (Degener, 1934) and as containing various numbers of species (Hillebrand, 1888) or just one species with different subtypes (Carlquist 1980). The genus Trematolobelia derives its name from its resemblance to Lobelia and for the unique morphology of its seed dispersal mechanism that has a porous morphology, trematos being the Greek term for hole. Trematolobelia is endemic to Hawaii with different types located on the main islands. The Hawaiians called these plants Koli’i (Wagner, 1990). There is no available record of their distinguishing between subtypes.

Currently the genus has been classified a member of the Campanulaceae family, sub-group Lobeliodeae. There are four species altogether: grandifolia, kauaiensis, macrostychus, and singularis (Wagner, 1990). There are two species of Trematolobelia at Kohala, grandifolia and macrostychus that Rock described as lustrialis and kohalaensis respectively. Kohalaensis is known from only one specimen collected by Rock in the early 20^th century (Wagner et. al.,1990) while grandifolia is relatively abundant at Kohala. It has also been reported from the saddle area between Mauna Kea and Mauna Loa and at Hawaii Volcanoes National Park (Wagner et. al.,1990). It has reportedly not been collected since 1966.

Hawaiian lobeliads have experienced adaptive radiation, exhibiting gigantism and arborescence (Carlquist, 1980). They appear to have experienced co-evolution with endemic honeycreeper birds that are believed to have been responsible for pollination.

White flowers with purple streaks distinguish grandifolia from the other species, which bear pink or red flowers (Wagner et. al. 1990). The plant grows as a single woody stem from which a rosette of lobate leaves emerges. The leaves have purple veins. Individual plants flower once before their death. As flowering commences, many of the leaves abscise at the apex as 4-5 radial horizontal branches develop, each bearing multiple flowers that develop first near the center. The corolla is white with faint purple streaks.

Hawaiian Lobeliodeae tend to bear fleshy fruits (Carlquist, 1980). In the case of

Trematolobelia, the fleshy fruit at the base of the flower decays leaving a porous skeleton. Inside seeds are protected in an envelope that persists until desiccation during dry weather, at which point the seeds are dispersed by the wind (Wagner et. al., 1990).

A thorough literature review of Trematolobelia will require that the researcher travel to Hawaii, Oahu, and Kauai as existing literature dealing specifically with Trematolobelia is limited in copies and not available for interlibrary loan. In fact, one may not find the most specific literature on the shelves as they are kept in the vault. In light of this, personal observations of are offered to the reader.

During the fall of 2001, grandifloria at Kohala was observed to be most numerous at ~1200m with the majority of flowering occurring in October but continuing through November. The majority of plants observed were less than one meter in height, although one was about a meter and another exceeded two meters tall. Their white inflorescences rise conspicuously in the dwarf brush. It appears to be an edge species growing on relatively open sloped ground devoid of taller trees and shrubs. Dry conditions were observed in late November when seeds began to fall from the plants in great numbers.

The author questions whether the flowering stalks could support the weight of a bird and has heard that white lobeliads were pollinated by native moths. The stalks persist for months so they must be pretty strong Alien wasps have been observed inspecting the flowers and may now play a role in pollination.

Incidentally after the individual (flowering cycle) pictured, decayed, four new recruits were observed, but also tibouchina which I pulled.

References

Carlquist, S. 1990. Hawaii a natural history. 247-248. National Tropical Botanical Garden. Lawai, HI

Degener, O. 1934. New illustrated flora of the Hawaiian islands. Hafner Publishing Company. New York and London

Hillebrand, W. 1965. Flora of the Hawaiian islands: A description of their phanerograms and vascular cryptograms. 236-239. Hafner Publishing Company. New York and London

Pratt, D. 1998. A pocket guide to Hawaii’s trees and shrubs: 98. Mutual Publishing

Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the flowering plants of Hawaii. V1: 485-481. University of Hawaii Press. Honolulu, HI