The Kneeland Prairie penny-cress is a perennial herb in the mustard family (Brassicaceae) that grows from 9.5 to 12.5 centimeters (3.7 to 4.9 inches) tall, with a basal cluster of leaves.  The margins of the basal leaves range from entire to toothed.  The white flowers have strongly ascending pedicels (flower stalks).  The fruit is a sharply pointed silicle (a short fruit typically no more than 2 to 3 times longer than wide). Kneeland Prairie penny-cress produces flowers from March to May.  Characteristics that separate Kneeland Prairie penny-cress (Noccaea fendleri ssp. californicum) from montane penny-cress (T. f. ssp. montanum) include the orientation of the flower stalks, shape and notching of the fruit, and length/width ratio of the fruit.  T. f. ssp. montanum has flower stalks perpendicular to the stem, not strongly ascending, and the silicles are either truncate or shallowly notched, but not acute at the apex as they are in Kneeland Prairie penny-cress.

Currently, the global distribution of the Kneeland Prairie penny-cress is restricted to three small patches of serpentine outcrop, encompassing about 2 acres of suitable habitat, within Kneeland Prairie, in Humboldt County, California.  Kneeland Prairie is a large prairie complex located about 12 miles inland from the Pacific Ocean, near the City of Eureka.  

The life history of Kneeland prairie penny-cress is poorly understood.  The plant normally begins blooming in March, with seed set in April or May and dehiscence of fruits (release of seeds) beginning in June.  Approximately 86 percent of the individual plants were reproductive in 1997 and 2001.  Absence of flowering was attributed to either grazing or immaturity.  Although the floral characteristics (white, small, and inconspicuous petals; anthers pointed in) of the genus are generally consistent with selfpollination, field and greenhouse observations of the closely related montane penny-cress suggest that species may be primarily an outbreeder.  Studies are needed to clarify the breeding system of Kneeland prairie penny-cress.  Seed germination and propagation requirements of Kneeland prairie penny-cress also not been well studied.

The single known population of Kneeland Prairie penny-cress occurs within Kneeland Prairie, located approximately 12 miles from the Pacific Ocean, and approximately 2,800 feet above mean sea level. Climate in the prairie is marine-influenced, with average annual precipitation estimated at 60 inches, and frequent summer fog.  Dominant plant species in its habitat typically include red fescue, common woolly sunflower, junegrass, large-fruited lomatium, and blue wildrye.  No shrubs or trees are present.

The plant only occurs on serpentine soils derived from ultramafic rocks such as serpentinite, dunite, and peridotite.  These rocks are found in discontinuous outcrops in the Sierra Nevada and Coast Ranges of California from Santa Barbara County to Humboldt County.  The chief constituent of the parent rock is a variant of iron-magnesium silicate.  Most serpentine soils are formed in place over the parent rock, and are therefore shallow, rocky, and highly erodible.  Serpentine soils, because of the parent material, tend to have high concentrations of magnesium, chromium, and nickel, and low concentrations of calcium, nitrogen, potassium, and phosphorus.  These characteristics make serpentine soil inhospitable for the growth of most plants, but some plants have adapted to serpentine substrates.

The single population of Kneeland Prairie penny-cress was last surveyed in 2002, and estimated at 8,800 individuals scattered among several outcrops, approximately 49 percent of which flowered that year.  Since then, the primary landowner has not authorized access to the majority of the population.   

Available habitat for Kneeland Prairie penny-cress in Kneeland Prairie has been significantly reduced over the past century as a result of construction of Mountain View Road, Kneeland Airport, and a fire helitack base.  The species is potentially threatened by future impacts related to proposed modifications to the airport and possible realignment of the road.  Due to its very restricted range, the species is also vulnerable to extinction from naturally occurring events such as fire, changes in grazing intensity, and other factors.  Two important tasks in recovery of the species include gaining authorized access for monitoring, and negotiation of a conservation mechanism ensuring future protection of the population and its habitat.  With these essential recovery tasks completed, the Fish and Wildlife Service will be able to document population trends, establish new colonies to reduce the threat of a catastrophic event, and conduct recovery efforts in general.

The greatest conservation need is continuing negotiations with the primary landowner to secure access to the site and the development of a conservation mechanism to protect the population and its habitat.  Establishment of new colonies is essential to the recovery effort, in order to compensate for the historical decline in the population and provide additional protection from catastrophic factors.  Initial enhancement efforts should focus on the existing exposed serpentine habitat.  Restoration of serpentine habitat, buried during past construction, may be pursued as opportunities arise. 

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