Hawaiian hibiscus are the seven known species of hibiscus regarded as native to Hawaiʻi. The yellow hibiscus is Hawaii's state flower. Although tourists regularly associate the hibiscus flower with their experiences visiting the US state of Hawaiʻi, and the plant family Malvaceae includes a relatively large number of species that are native to the Hawaiian Islands, those flowers presented to or regularly observed by tourists are generally not the native hibiscus flowers. Most commonly grown as ornamental plants in the Islands are the Chinese hibiscus (Hibiscus rosa-sinensis) and its numerous hybrids.
The native plants in the genus Hibiscus in Hawaiʻi are thought to have derived from four independent colonization events: two for the five endemic species (four closely related species plus the yellow-flowered species) and one each for the two indigenous species.
The native hibiscus (genus Hibiscus) found in Hawaiʻi are:
- Hibiscus arnottianus A. Gray – kokiʻo keʻokeʻo ("kokiʻo that is white like the shine of silver") is an endemic species of hibiscus with white flowers. Three subspecies are recognized: H. arnottianus arnottianus found in the Waiʻanae Range of western Oʻahu; H. a. immaculatus which is very rare (listed as endangered) on Molokaʻi; and H. a. punaluuensis from the Koʻolau Range on Oʻahu. Perhaps only a dozen plants of H. a. immaculatus exist in nature in mesic and wet forests. This species is closely related to H. waimeae, and the two are among the very few members of the genus with fragrant flowers. It is sometimes planted as an ornamental or crossed with H. rosa-sinensis. In the Hawaiian language, the white hibiscus is known as the pua aloalo.
- Hibiscus brackenridgei A. Gray – maʻo hau hele ("hau most similar to maʻo") is a tall shrub (up to 10 m or 33 ft) with bright yellow flowers, closely related to the widespread H. divaricatus. Two subspecies are recognized: H. b. brackenridgei, a sprawling shrub to an erect tree found in dry forests and low shrublands at elevations of 400–2,600 ft (120–790 m) above sea level on Molokaʻi, Lānaʻi, Maui, and Hawaiʻi; and H. b. mokuleianus, a tree from dry habitats on Kauaʻi and the Waiʻanae Range on Oʻahu. This species is listed as an endangered species by the USFWS. The yellow flower of this species was made the official state flower of Hawaiʻi on 6 June 1988, and although endangered in its natural habitats, has become a moderately popular ornamental in Hawaiian yards.
- Hibiscus clayi O.Deg. & I.Deg. is an endemic shrub or small tree with bright red flowers, generally similar to H. kokio, and found in nature on Kauaʻi in dry forests. It is listed as endangered by USFWS.
- Hibiscus furcellatus Desr. is a pink-flowered hibiscus considered an indigenous species, typically found in low and marshy areas of the Caribbean, Florida, Central and South America, and Hawaiʻi, where it is known as ʻakiohala, ʻakiahala, hau hele, and hau hele wai ("entirely puce hau").
- Hibiscus kokio Hillebr., kokiʻo or kokiʻo ʻula ("red kokiʻo") is a shrub or small tree (3–7 m or 9.8–23 ft) with red to orangish (or rarely yellow) flowers. This endemic species is not officially listed, but considered rare in nature. Two subspecies are recognized: H. kokio kokio found in dry to wet forests on Kauaʻi, Oʻahu, Maui, and possibly Hawaiʻi at elevations of 70–800 m (230–2,600 ft); and H. k. saintjohnianus from northwestern Kauaʻi at elevations of 150–890 m (490–2,920 ft).
- Hibiscus tiliaceus L., hau, is a spreading shrub or tree common to the tropics and subtropics, especially in coastal areas. This species is possibly indigenous to Hawaiʻi, but may have been introduced by the early Polynesians.
- Hibiscus waimeae A.Heller, kokiʻo keʻokeʻo or kokiʻo kea ("kokiʻo that is white as snow"), is a Hawaiian endemic, gray-barked tree, 6–10 m (20–33 ft) tall, with white flowers that fade to pink in the afternoon. Two subspecies are recognized: H. waimeae hannerae (rare and listed as endangered) found in northwestern valleys of Kauaʻi, and H. w. waimeae occurring in the Waimea Canyon and some western to southern valleys on Kauaʻi. This species closely resembles H. arnottianus in a number of characteristics.
In addition to the species of Hibiscus listed above, flowers of several other related Hawaiian plants of the family Malvaceae resemble Hibiscus flowers, although are generally smaller. The endemic genus, Hibiscadelphus, comprises seven species described from Hawaiʻi. Three of these are now thought to be extinct and the remaining four are listed as critically endangered or extinct in the wild. Another endemic genus, Kokia, comprises four species of trees. All but one (K. kauaiensis) are listed as either extinct or nearly extinct in the wild.
Three endemic species of the pantropical genus, Abutilon occur in Hawaiʻi: A. eremitopetalum, A. menziesii, and A. sandwicense; all are listed as endangered. Cotton plants (Gossypium spp.), whose bright yellow flowers are certainly hibiscus-like, include one endemic: G. tomentosum, uncommon but found in dry places on all the main islands except Hawaiʻi. The widespread milo (Thespesia populnea) is an indigenous tree with yellow and maroon flowers.
- Wagner,, W.L.; Herbst, D.R.; Sohmer, S.H. (1999). Manual of the flowering plants of Hawai'i (Revised ed.). Honolulu, Hawaii: University of Hawaii Press. ISBN 0-8248-2166-1.
- Barboza, Rick (2003-01-03). "Kokiʻo Keʻo Keʻo". Honolulu Star-Bulletin.
- Little Jr., Elbert L.; Roger G. Skolmen (1989). Kokiʻo keʻokeʻo, native white hibiscus (PDF). United States Forest Service.
- "Hibiscus brackenridgei subsp. brackenridgei". Meet the Plants. National Tropical Botanical Garden. Retrieved 2009-03-11.
- "Hawaii State Flower". NETSTATE.COM. 2009-09-28. Retrieved 2009-10-30.
- "Hibiscus kokio subsp. kokio". Meet the Plants. National Tropical Botanical Garden. Retrieved 2009-03-11.
- "Hibiscus kokio subsp. saintjohnianus". Meet the Plants. National Tropical Botanical Garden. Retrieved 2009-03-11.