Lepidium barnebyanum is a rare species of flowering plant in the mustard family

Brassicaceae

Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....

 known by the common names Barneby's pepperweed, Barneby's pepper-grass, and Barneby's ridge-cress. It is endemic to Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, where there is a single population in Duchesne County

Duchesne County, Utah

Duchesne County is a county located in the U.S. state of Utah. As of 2010 the population was 18,607, a 29.5% increase over the 2000 figure of 14,371. Its county seat is Duchesne and the largest city is Roosevelt.-Geography:...

. It is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of the United States.

This is a clumpy perennial herb with a woody caudex

Caudex

A caudex is a form of stem morphology appearing as a thickened, short, perennial stem that is either underground or near ground level . It may be swollen for the purpose of water storage, especially in xerophytes...

 at the base layered with new leaves and the remains of previous seasons' leaves. The stems grow less than 20 centimeters tall. The leaves are linear in shape and one half centimeter to eight centimeters in length. Most are at the caudex and there are a few smaller ones higher on the stems. The inflorescence

Inflorescence

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

 is a raceme

Raceme

A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...

 of many white, cream, or yellowish flowers. Blooming occurs in April and May through June.

This plant grows in pinyon-juniper woodland

Pinyon-juniper woodland

A Pinyon-juniper woodland is a forest type characteristic of many parts the Western United States, often in higher elevations of desert ecoregions.-Locations:...

 and desert scrub on rock outcrops in white shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

 formations. There are petroleum

Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 deposits under the rock. Common plants in the area include Colorado Pinyon

Colorado Pinyon

The Colorado Pinyon, Two-needle Pinyon, or Piñon Pine, ', is a pine in the pinyon pine group whose ancestor was a member of the Madro-Tertiary Flora and is native to the United States....

 (Pinus edulis), Utah juniper

Juniperus osteosperma

Juniperus osteosperma is a shrub or small tree reaching 3-6 m tall. It is native to the southwestern United States, in Utah, Nevada, Arizona, western New Mexico, western Colorado, Wyoming, southern Montana, southern Idaho and eastern California...

 (Juniperus osteosperma), Hooker's sandwort (Arenaria hookeri), spiny phlox (Phlox hoodii), Colorado feverfew (Parthenium ligulatum), large-flowered goldenweed (Haplopappus armerioides), stemless hymenoxys (Hymenoxys acaulis), Bateman's buckwheat (Eriogonum batemanii), and table Townsend daisy (Townsendia mensana).

There is one known population of this plant containing about 5000 individuals. The population occurs on a shale substrate that is popular with off-road vehicle

Off-road vehicle

An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...

enthusiasts whose vehicles damage the habitat. Petroleum exploration is also a threat.