William Hillebrand

Zanthoxylum hawaiiense, commonly known aʻe or Hawaiʻi pricklyash, is a species of flowering plant in the family Rutaceae, that is endemic to Hawaii. It can be found at elevations of 550–1,740 m (1,800–5,710 ft) in dry forests, where it grows on lava flows, and mixed mesic forests on the Island of Hawaiʻi, Maui, Molokaʻi, and Lānaʻi. It is threatened by habitat loss. Zanthoxylum is from the Greek ξανθὸν ξύλον, meaning "yellow wood." This is the only genus in the citrus family (Rutaceae) with a pantropical distribution. Zanthoxylum also colonized several Pacific Islands and the Hawaiian clade

Haplostachys (honohono) is a genus of flowering plants in the mint family, Lamiaceae, first described as a genus in 1888. The entire genus is endemic to the Hawaiian Islands, although 4 of the 5 known species that have been placed in the genus are now believed to be extinct, the fifth listed as "Critically Imperiled." Species †Haplostachys bryanii Sherff - Molokai but apparently extinct Haplostachys haplostachya (A.Gray) H.St.John - Kauai, Maui, Hawaii; Critically Imperiled †Haplostachys linearifolia (Drake) Sherff - Maui, Molokai but apparently extinct on both islands †Haplostachys munroi

Alphitonia ponderosa is a species of flowering tree in the family Rhamnaceae, that is endemic to the Hawaiian Islands. It is locally known as kauila, as is the related Colubrina oppositifolia.

Acacia koaia, known as koaiʻa or koaiʻe in Hawaiian, is a species of acacia that is endemic to Hawaii. It is closely related to koa (Acacia koa), and is sometimes considered to be the same species.

Zanthoxylum oahuense, commonly known as aʻe or Oʻahu prickly-ash, is a species of flowering plant in the family Rutaceae, that is endemic to the island of Oʻahu in Hawaii. It is a small tree, reaching a height of 5 m (16 ft). Aʻe inhabits mixed mesic and wet forests at elevations of 580–800 m (1,900–2,620 ft). It is threatened by habitat loss.

Wikstroemia villosa, the hairy wikstroemia or hairy false ohelo, is a tropical species of plant in the Thymelaeaceae family.

Achyranthes is a genus of medicinal and ornamental plants in the amaranth family, Amaranthaceae. Chaff flower is a common name for plants in this genus. The Hawaiian species (A. divaricata, A. humile, and A. sandwicensis) are known in Hawaiian as kuluʻī. A 2024 morphological and phylogenetic analysis by Vanessa Di Vincenzo et al. merged the genus Achyropsis and the Hawaiian genus Nototrichium into Achyranthes to make it monophyletic. The genus is characterized by solitary, fertile flowers.

Cyperus hypochlorus, commonly known as the Oahu flatsedge, is a species of sedge that is native to parts of Hawaii.

Santalum haleakalae, known as Haleakala sandalwood or ʻIliahi in Hawaiian, is a species of flowering tree in the sandalwood family, that is endemic to the islands of Maui, Lanai, and Molokai in the Hawaiian Islands, part of the United States. It grows in subalpine shrublands at elevations of 1,900 to 2,700 m (6,200 to 8,900 ft), especially on the slopes of Haleakalā.

Cyrtandra wawrae, the rockface cyrtandra, is a species of flowering plant in the family Gesneriaceae, native to Kauai, Hawaii. A shrub reaching 10 ft (3 m), it is often found growing on rock walls.

Cyanea procera is a rare species of flowering plant in the bellflower family known by the common name Molokai cyanea. It is endemic to Hawaii, where it is known only from the island of Molokaʻi. It is a federally listed endangered species of the United States. Like other Cyanea it is known as haha in Hawaiian. This plant has been reduced to very low numbers. At one time it was thought to be extinct. By 1992 there were four plants known. By 2005 there was only a single plant of this species existing in the wild. Plant propagation efforts have not been successful. This Hawaiian lobelioid is a

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Carex montis-eeka, the Molokai sedge, is a species of flowering plant in the family Cyperaceae, native to Hawaii. There it is found in bogs.

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Wikstroemia bicornuta, the alpine false ohelo, is a species of flowering plant in the mezereon family, Thymelaeaceae, that is endemic to Hawaii. It inhabits mixed mesic and wet forests at elevations of 900–1,050 m (2,950–3,440 ft) on the islands of Lānaʻi and Maui. It is threatened by habitat loss.

Phyllostegia hispida, the hispid phyllostegia, is an endangered species of flowering plant in the mint family, Lamiaceae. It is found only in wet forests at elevations of 2,300–4,200 feet (700–1,280 m) on the island of Molokaʻi in Hawaiʻi. This green vine's loosely spreading branches often form a large mass.

Achyranthes humilis is a rare species of flowering plant in the family Amaranthaceae known by the common names kaala rockwort and kulu'i. It is endemic to Hawaii, where it is now limited to the island of Oahu, having been extirpated from Maui. It is a federally listed endangered species of the United States. The main threat to the species is fire. Most populations occur on the Makua Military Reservation in the Waianae Range of Oahu, in territory at high risk for fire. Other threats include damage to the habitat by feral goats, and competition with introduced species of plants, such as

Mezoneuron kauaiense is a rare shrub or small tree in the genus Mezoneuron (pea family, Fabaceae), that is endemic to Hawaii. Common names include uhiuhi (the Big Island and Kauaʻi), kāwaʻu (Maui), and kea (Maui). It is threatened by invasive species, particularly feral ungulates.

Lobelia hypoleuca, common names kuhiʻaikamoʻowahie, 'ōpelu, liua, or mo'owahie, is one of several species in the genus Lobelia endemic to Hawaii though cultivated elsewhere. It is found in nature on the islands of Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui and Hawaiʻi. Lobelia hypoleuca is a shrub that can attain a height of 3.3 m (11 feet). Stems are woody, whitish, with a rough texture. Leaves are narrowly lanceolate with teeth along the margins, up to 60 cm (2 feet) long, green and shiny above, but appearing white on the underside due to a dense covering of fine wooly hairs (hence the epithet

Gouania hillebrandii, also known as hairyfruit chewstick, is an endangered species of Gouania that is endemic to Hawaii. It formerly could be found on Maui, Molokaʻi, Lānaʻi and Kahoʻolawe, but is today restricted to western Maui near Lahaina. It inhabits dry forests at elevations of 244–518 m (801–1,699 ft). Hairyfruit chewstick is a single branched shrub with small, white flowers. The plant is federally listed as an endangered species of the United States.

Cyanea platyphylla is a rare species of flowering plant in the bellflower family known by the common names puna cyanea and flatleaf cyanea. It is endemic to the island of Hawaii, where there are fewer than 100 plants remaining in the wild. It is a federally listed endangered species. Like other Cyanea it is known as haha in Hawaiian. This Hawaiian lobelioid is a shrub reaching 3 meters in maximum height. It bears white, red, or red-striped yellowish flowers. The plant grows in wet forests, including those on the eastern slopes of Mauna Loa, Mauna Kea, and Kīlauea. It is threatened by

Cyanea asplenifolia is a flowering plant in the Campanulaceae family. The IUCN has classified the species as critically endangered. It is native to the Hawaiian Islands.

Cyanea angustifolia is a shrub in the genus Cyanea that is endemic to Hawaiʻi. In Hawaiʻi, it is referred to as ʻAku as well as Hāhā, which is the term for the generalized Cyanea genus. C. angustifolia was a food source during times of food scarcity for the Hawaiians. This shrub is characterized by specialized flower shapes and it is found at higher elevations in wet environments.

Cyanea acuminata is a rare species of flowering plant known by the common names Honolulu cyanea. It is endemic to Oahu, where there are no more than 250 individuals remaining. 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 up to 2 meters tall. It grows in wet forests and on slopes and ridges in the Koʻolau and Waiʻanae Mountains of Oahu. The remaining plants are divided among 18 subpopulations which are threatened by damage to their habitat from feral pigs and goats, rats, and exotic

Coprosma montana, the pilo, is a species of flowering plant in the family Rubiaceae, native to Hawaii. A shrub or small tree, it is found growing at elevations of 6,000 to 10,000 ft (1,800 to 3,000 m).

Clermontia pyrularia is a rare species of flowering plant in the bellflower family known by the common names Hamakua clermontia and pear clermontia. It is one of several Hawaiian lobelioids in genus Clermontia that are known as ʻoha wai and haha. It is endemic to the island of Hawaiʻi, where there is one remaining wild population containing 15 individuals and several propagated individuals that have been planted in protected habitat. This is a federally listed endangered species of the United States. This is a small tree which grows in Metrosideros polymorpha and Acacia koa dominated montane

ʻAhakea or Hawaiʻi dogweed (Bobea sandwicensis) is a species of flowering tree in the coffee family, Rubiaceae, that is endemic to Hawaiʻi. It inhabits lava plains as well as dry, coastal mesic and mixed mesic forests at elevations of 100–1,220 metres (330–4,000 ft) on the islands of Oʻahu, Molokaʻi, Lānaʻi, and Maui. It is threatened both by habitat loss and competition from invasive species.

Argyroxiphium virescens was a species of flowering plant in the family Asteraceae that was last seen in 1945. It was found only in the Hawaiian Islands where it was endemic to the eastern part of Maui. Its natural habitats were subtropical or tropical moist montane forests and subtropical or tropical high-altitude shrubland. It is officially declared extinct, but in 1989 plants were discovered that appear to be hybrids between it and the Haleakalā silversword. This hybrid is known as the Pu'u 'Alaea greensword.

Stenogyne bifida is a rare species of flowering plant in the mint family known by the common name twocleft stenogyne. It is endemic to Hawaii, where it is known only from the island of Molokai. In 2010, there was only a single individual remaining in the wild; this is a seedling. It is a federally listed endangered species of the United States. This plant is a climbing, trailing perennial vine. It produces yellow-green to brownish flowers. It grows in disturbed forest habitat dominated by Metrosideros polymorpha. The area has a large population of feral pigs that damage the habitat. The plant

Silene alexandri is a rare species of flowering plant in the family Caryophyllaceae known by the common names Kamalo Gulch catchfly and Alexander's catchfly. It is endemic to Hawaii, where it is known only from the island of Molokai. It is threatened by the degradation of its habitat and it is a federally listed endangered species of the United States. This subshrub grows 30 to 60 centimetres (12 to 24 inches) tall and bears white flowers. It grows in moist lowland shrubland on the sides of steep basalt cliffs. The plant has only been seen on a stretch of the island of Molokai 4 kilometres