Charles Noyes Forbes

Viola oahuensis is a rare species of flowering plant in the violet family known by the common name Oahu violet. The species is endemic to Hawaii, where it is known only from the Koolau Range on the island of Oahu. It grows along the upper ridges of the Koolau Mountains where the most rain falls. It is cultivated as an ornamental plant on the island.

Exocarpos luteolus is a rare species of flowering plant in the sandalwood family known by the common names leafy ballart or heau. It is endemic to Hawaii, where it is known only from the island of Kauai. There are eight populations remaining, for a total global population of only 39 individuals. The plant was federally listed as an endangered species of the United States in 1994. This plant is a shrub growing one half to two meters tall. There are two types of leaves, lance-shaped to oval leaf blades up to 8 centimeters long and smaller, reduced leaves that are like scales. Some plants have

Euphorbia rockii (syn. Chamaesyce rockii) is a rare species of flowering plant in the euphorb family known by the common names Koolau Range sandmat and Rock's broomspurge. It is endemic to Oʻahu, Hawaii, where it is known only from the Koʻolau Mountains. There are 200 to 300 plants remaining. Like other Hawaiian euphorbs, this plant is known locally as ʻakoko. The remaining plants exist in fewer than 10 subpopulations on the peaks of the Koʻolau Mountains, where they often grow in wet forests and shrublands. The plant is threatened by the destruction and degradation of its habitat. The main

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Clermontia samuelii is a rare species of flowering plant in the bellflower family known by the common name Hana clermontia. It is one of several Hawaiian lobelioids in genus Clermontia that are known as `oha wai. This plant is endemic to Maui, where there are fewer than 250 mature specimens remaining. This is a federally listed endangered species of the United States. This is a shrub which can reach five meters in height. It grows in wet Metrosideros forests. Some individuals are protected within Haleakalā National Park. Threats to the species include invasive plant species such as glory bush

Viola helena, commonly known as Wahiawa stream violet, is a rare species of flowering plant in the violet family. It is endemic to Hawaii, where it is known only from the Wahiawa Mountains of Kauai. It is threatened by exotic plant species and feral pigs. It is a federally listed endangered species of the United States.

Lysimachia filifolia is a rare species of flowering plant in the Primulaceae known by the common name Wailua River yellow loosestrife. It is endemic to Hawaii, where there are two populations on Oahu and one on Kauai. It is a federally listed endangered species of the United States. This is a small shrub growing up to about half a meter in maximum height. The leaves are very narrow to threadlike and the flowers are reddish purple. The plant grows on the faces of waterfalls in wet forest habitat. There are about 130 individuals remaining on the island of Oahu, growing at waterfalls in the

Hibiscadelphus bombycinus, the Kawaihae hibiscadelphus, is an extinct species of flowering plant in the mallow family, Malvaceae. It was endemic to the Kohala mountain on the island of Hawaiʻi, in the U.S. state of Hawaii. It has not been collected since 1865. It is presumed to have been extinct since 1920.

Cyrtandra munroi is a rare species of flowering plant in the African violet family known by the common names Lanaihale cyrtandra and Munro's cyrtandra. It is endemic to Hawaii, where it is known from the islands of Lanai and Maui. There are fewer than 50 individuals remaining in the wild. It is a shrub with hairy leaves and white flowers. It was federally listed as an endangered species in 1992. Like other Hawaiian Cyrtandra it is called ha`iwale. The wet forests where this plant occurs are destroyed and degraded by several processes, such as deer and exotic plant species.

Cyanea undulata is a rare species of flowering plant in the bellflower family known by the common names wavy cyanea and leechleaf cyanea. It is endemic to the island of Kauai, where it is in rapid decline. It is a federally listed endangered species of the United States. Like other Cyanea it is known as haha in Hawaiian. This Hawaiian lobelioid is a shrub which can exceed three meters in height. The leaves have wavy edges and the flowers are yellow. The plant was first described in 1909 and then it was not seen again until it was rediscovered in 1991. In 1994 there was a single population

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Argyroxiphium caliginis, the ʻEke silversword, is a species of flowering plant in the family Asteraceae. It is found only in two Hawaiian tropical rainforest bogs in West Maui, Hawaiʻi. The species is threatened by damage to the bogs by rooting feral pigs, but the main population at ʻEke Crater is now protected by fencing.

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Hesperomannia lydgatei, the Kauaʻi island-aster or Kauaʻi hesperomannia, is a rare species of flowering plant in the family Asteraceae. It is found only in Hawaii, where it is endemic to Kauaʻi. It is threatened by habitat loss. There are fewer than 300 individuals remaining.

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Polyscias racemosa, or false 'ohe, is a species of flowering plant in the family Araliaceae. As Munroidendron racemosum, the species was until recently considered to be the only species in the monotypic genus Munroidendron. With the change in classification, Munroidendron is now obsolete. Polyscias racemosa is endemic to the Hawaiian island of Kauai. It is very rare in the wild and some of its original habitat has been replaced by sugar cane plantations. It was thought for some time to be probably extinct, but was rediscovered a few years prior to 1967. Using cladistic methods, phylogenetic

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Geniostoma lydgatei, the Wahiawa Mountain labordia, is a species of flowering plant in the Loganiaceae family. It is endemic to the Hawaiian Islands, where it is present only in the Wahiawa Mountains of Kauai. It is threatened by habitat loss.

Argyroxiphium × kai, commonly known as the Kai silversword, is a hybrid species of silversword plant in the family Asteraceae, and is a part of the silversword alliance. The name derived from the Hawaiian word "kai", which translates to "sea". It was described by David D. Keck in 1936. Argyroxiphium × kai is a natural hybrid between Argyroxiphium caliginis and Argyroxiphium grayanum, so the name Argyroxiphium calignis × grayanum can also apply, but is generally less common. It is endemic to Maui, Hawaii, where it grows between other Argyroxiphium species, primarily the two species that

Helodeaster erici is a species of flowering plant from the genus Helodeaster. It is endemic to the island of Kauai in the Hawaiian Islands. The species was originally described by Charles Noyes Forbes as Lagenophora erici in 1918. In 2020 Guy L. Nesom placed it in the new Hawaiian endemic genus Helodeaster.

Geniostoma kaalae, the Waianae Range labordia, is a species of flowering plant in the Loganiaceae family. It is endemic to the Waiʻanae Range on Oahu island in Hawaii. It is an endangered species threatened by habitat loss.