One of spectacular flowers found in the Northern Koʻolau Mountains of Oʻahu is Koliʻi — Tremtolobelia macrostachys — which often grows as an epiphyte on other plants in the native landscape.
According to Joseph Rock, who wrote the monograph on the Hawaiian Lobeliad Group in 1919, the Hawaiian name koliʻi applies to Tremtolobelia kauaiensis which is not this plant. But in modern times the name has been extended to other Trematolobelia species as well.
One of the unusual things about this koliʻi is how wide spread it is. Tremtolobelia macrostachys is endemic to the Hawaiian Islands and is known on Oʻahu, Molokai, Maui, Lanai and Hawaiʻi but has subsequently become extinct on Lanai and Hawaiʻi. [Wikipedia says that Tremtolobelia macrostachys is no longer found on Hawaii Island but Melora Purrell from the Kohala Watershed Partnership reports that it is still found on Kohala Mountain]. The vast majority of plants in the Hawaiian Lobeliad Group are endemic to a single island — with just a few found on adjacent islands. Tremtolobelia macrostachys is not endangered and is the most numerous of the Hawaiian Lobeliads. Its future is relatively secure unlike many other Hawaiian Lobeliads.
Tremtolobelia macrostachys is amazing for the sheer number of flowers it produces when it blooms which is usually around November to January. The plant produces multiple spays of pink flowers on candelabra-like stalks. This koliʻi often has 4-5 flower stalks but large plants can have 16 or more sprays of flowers at a time. The flowers have irregularly shaped petals that often curl backwards and a stamenal column that tilts forward.
When the flowers first open the male part of the flower — stamens (white brushes) — come out first. Only after the pollen is spent does the female part of the flower — stigma (green pursed lips) — emerge. The flowers are pollinated by native birds and insects but in more recent times bees and other introduced creatures pollinate them too.
There is a closely related koliʻi sub-species in the Waiʻanae Mountains — Tremtolobelia kaalae — which looks very similar but blooms at a different time of year — around April to June — and has other subtle differences — its flowers are often a deeper shade of magenta.
The Hawaiian Lobeliad Group — which consist of 6 genera and 126 species — is in the bellflower family, Campanulaceae, and is endemic to the Hawaiian Islands. The following 6 genera are in the group.
- Lobelia (13 species)
- Trematolobelia (4 species)
- Cyanea (75 species)
- Clermontia (22 species)
- Delissea (10 species)
- Brighamia (2 species)
The Hawaiian lobeliad group is viewed by botanists as the pinnacle of adaptive radiation in plants. The group evolved the most species from a single colonization in an oceanic archipelago. The group was long thought to have originated from at least three introductions: one for Lobelia and Trematolobelia, one for Brighamia, and one for Clermontia, Cyanea, and Delissea. But based on recent genetic evidence it is now believed that all are derived from a single introduction.
Trematolobelia are very similar to lobelia, but differs in one important aspect — seed dispersal. After the flowers are pollinated the seeds develop within the green bulbous calyx at the bottom of the flowers. When the calyx dries out holes appear in the capular walls and allow the seeds to fall out when shaken by the wind.
A Monographic Study of the Hawaiian Species of Tribe Lobelioideae Family Campunulaneae, By Joseph Francis Rock, Bishop Musuem Press 1919
Origin, adaptive radiation and diversification of the Hawaiian lobeliads (Asterales: Campanulaceae) by Thomas J. Givnish, Kendra C. Millam, Austin R. Mast, Thomas B. Paterson, Terra J. Theim, Andrew L. Hipp, Jillian M. Henss, James F. Smith, Kenneth R. Wood and Kenneth J. Sytsma, The Royal Society, 2008
Hawaiian Lobelioids, Wikipedia
Hawaiian Native Plant Genera – Campanulaceae, University of Hawaii, Department of Botany