'ōhā wai

The Hawaiian lobelioids are a group of flowering plants in the bellflower family, Campanulaceae, subfamily Lobelioideae, all of which are endemic to the Hawaiian Islands. This is the largest plant radiation in the Hawaiian Islands, and indeed the largest on any island archipelago, with over 125 species. The six genera involved can be broadly separated by growth habit: Clermontia are typically branched shrubs or small trees, up to 7 metres (23 ft) tall, with fleshy fruits; Cyanea and Delissea are typically unbranched or branching only at the base, with a cluster of relatively broad leaves at the apex and fleshy fruits; Lobelia and Trematolobelia have long thin leaves down a single, non-woody stem and capsular fruits with wind-dispersed seeds; and the peculiar Brighamia have a short, thick stem with a dense cluster of broad leaves, elongate white flowers, and capsular fruits. The relationships among the genera and sections remains unsettled as of April 2022.

Many species have beautiful and spectacular flowers, especially those in Lobelia and Trematolobelia. They are also highly vulnerable to feeding by feral ungulates such as feral pigs; the stems are only partly woody, and contain few defenses against herbivory. The bark contains a milky (but apparently non-poisonous) latex, and is often chewed by rats and pigs. Seedlings are also vulnerable to disturbance by pig digging, and in areas with high densities of pigs it is not uncommon to find the only lobelioids being epiphytic on larger trees or on fallen logs.