''Lepidium arbuscula'' is a rare species of flowering plant in the

mustard family Brassicaceae () or (the older but equally valid) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some ar ...

known by the common names ''`anaunau'' and Waianae Range pepperwort. It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, where it is known only from the

Waianae Mountains Waianae () is a census-designated place (CDP) in the City and County of Honolulu, Hawaii, United States. As of the 2020 census, the CDP population was 13,614. Its name means "waters of the mullet". Its etymology is shared with the far northe ...

on the island of

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

. In 2003 there were ten populations remaining with fewer than 1000 individuals in total.USFWS
''Lepidium arbuscula'' Five-year Review.
July 2009. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

of the US. This is a

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

growing to a maximum height near 1.2 meters. The leaves are clustered around the ends of the gnarled branches.''Lepidium arbuscula''.
The Nature Conservancy. Little is known about the biology of the species. It is threatened by the loss and degradation of its habitat, which is mainly due to the presence of

feral A feral (; ) animal or plant is one that lives in the wild but is descended from domesticated individuals. As with an introduced species, the introduction of feral animals or plants to non-native regions may disrupt ecosystems and has, in som ...

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

s such as

goat The goat or domestic goat (''Capra hircus'') is a species of Caprinae, goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the ...

s and

pigs The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

, and introduced plant species such as fire tree (''Morella faya'').

References

arbuscula Endemic flora of Hawaii Biota of Oahu Waianae Range Plants described in 1888 {{Brassicales-stub