''Thlaspi californicum'' is a rare species of flowering plant in the family

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

known by the common name Kneeland Prairie penny-cress. 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 ...

to California, where it is known from only one stretch of grassland in Humboldt County. It is threatened by development. 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 United States. The

taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

of this species is uncertain. Authors call it ''Thlaspi californicum'',''Thlaspi californicum''.
''Jepson Manual Treatment''. Retrieved August 17, 2011.''Thlaspi californicum''.
''The Nature Conservancy''. Retrieved August 17, 2011.Kneeland Prairie penny-cress (''Thlaspi californicum'') 5-Year Review: Summary and Evaluation.
''USFWS'' (June 2006). Retrieved August 16, 2011. ''Thlaspi montanum'' var. ''californicum'',''Thlaspi californicum''.
''CalFlora''. Retrieved August 17, 2011. ''Noccaea californica'',''Noccaea californica''.
USDA Plants Profile. Retrieved August 17, 2011. and ''Noccaea fendleri'' ssp. ''californica'',''Noccaea fendleri'' ssp. ''californica''.
''Flora of North America''. Retrieved August 17, 2011. and there are other

synonyms A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

. This plant is a perennial herb growing roughly 10 centimeters tall, the height varying from 1 to 20 centimeters. There are spatula-shaped lower leaves a few centimeters long and a few leaves higher on the plant. The

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

is a

raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...

of mustardlike flowers with white spoon-shaped petals just under a centimeter in length. The fruit is a

silique A silique or siliqua (plural ''siliques'' or ''siliquae'') is a type of fruit (seed capsule) having two fused carpels with the length being more than three times the width. When the length is less than three times the width of the dried fruit ...

. The plant often reproduces vegetatively by

cloning Cloning is the process of producing individual organisms with identical genomes, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction; this reproduction of an organism by itself without ...

. As of 2000 there was only one population of this plant. It is located adjacent to the

Kneeland Airport Kneeland Airport is a public airport operated by Humboldt County southeast of Eureka, California. Located on a mountain ridge at over above sea level, this airfield is used by general aviation aircraft, which sometimes seek an alternate airp ...

on the Kneeland Prairie near

Eureka Eureka often refers to: * Eureka (word), a famous exclamation attributed to Archimedes * Eureka effect, the sudden, unexpected realization of the solution to a problem Eureka or Ureka may also refer to: History * Eureka Rebellion, an 1854 g ...

in Humboldt County. In the area there are three colonies growing on separate serpentine

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s on the prairie. Two of the colonies are separated by the Kneeland Airport. The plant is limited to the

serpentine soil Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially an ...

s of the local landscape. This plant is threatened by development at the airport and other facilities nearby, including roads and a

helitack Helitack crews are teams of wildland firefighters who are transported by helicopter to wildfires. Helicopters provide rapid transport, enabling helitack crews to quickly respond and assess a wildfire situation. Helitack crews may land near a w ...

base. In the past few decades the amount of available habitat has been decreased 50% or more, possibly as much as 70%. It has also led to

habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological proces ...

as the population is bisected by the airport and the road. Planned expansion projects at the airport, including installation of a

parking lot A parking lot or car park (British English), also known as a car lot, is a cleared area intended for parking vehicles. The term usually refers to an area dedicated only for parking, with a durable or semi-durable surface. In most jurisdi ...

, may reduce the amount of suitable habitat further.

References

External links

''Thlaspi californicum''.
CalPhotos. {{Taxonbar, from=Q7786579 Brassicaceae Endemic flora of California