CPC National Collection Plant Profile

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CPC National Collection Plant Profile

Rhynchospora knieskernii

Common Names: 
Kneiskern's beaked sedge, Knieskern's beaked rush
Growth Habit: 
CPC Number: 


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 Fish & WildLife

Rhynchospora knieskernii is Fully Sponsored
Primary custodian for this plant in the CPC National Collection of Endangered Plants is: 
Elizabeth J. Farnsworth contributed to this Plant Profile.

Rhynchospora knieskernii

Rhynchospora kneiskernii is a grass-like plant of the Sedge family that grows only in the Pinelands of New Jersey. A short-lived perennial, the plant inhabits disturbed, open, early-successional wet areas in gravel and clay pits, power-line and railroad rights-of-way, recent burns, muddy swales, and cleared areas. The largest populations occur on natural bog iron deposits in the Pine Barrens. Periodic disturbances and fluctuating groundwater levels appear necessary to perpetuate its existence, as it is a poor competitor with other plants. Thus, succession to shrubs and forest threaten the plant, as well as irreversible disturbances brought by land development, trampling and soil compaction cause by intensive off-road vehicle use, and lowered water levels caused by water withdrawal and drought.

Research and Management Summary:
While little research has been performed directly on this species, a recovery plan has been written for this federally threatened plant. Unfortunately, most populations of this plant are located on private land. However, the U.S. Fish and Wildlife Service has been working to maintain the health of the species through management of federally-owned lands where it is found.

Plant Description:
Rhynchospora kneiskernii grows to 60 cm in height, with many slender stems issuing from the base. Its narrow leaves (only 1 to 2 mm wide) often roll inward. Numerous small spikelets of flowers occur at widely separated intervals along the stem. The plant is called "beaked-rush" because the beak at the base of the persistent style is nearly half as long as the 1.3 mm-long fruit (achene) itself.

Distribution & Occurrence

State Range
New Jersey
State Range of  Rhynchospora knieskernii
  Rhynchospora kneiskernii occurs in groundwater-influenced, constantly fluctuating, successional environments (USFWS 1993). The plant was once thought to be closely associated with natural bog iron deposits in the Pinelands (Stone 1911), but has now been found in a wider variety of environments. Bog iron forms when slow-moving, acidic stream water leaches iron from the Cretaceous outwash soils characteristic of the Pinelands. Upon contact with oxygen and oxidizing bacteria, the iron mobilizes and is re-deposited in hard layers of "iron stone" in streambeds and adjacent floodplain wetlands. Continual stream erosion and challenging soil chemistry tend to inhibit growth of trees and shrubs that would normally shade out Rhynchospora kneiskernii (USFWS 1997). Six of the 38 known extant populations of the plant occur on this unusual substrate.

Most of the populations, however, have opportunistically colonized newly-disturbed wet areas, including: the edges of abandoned pits and gravel, clay, and sand mines; unpaved roads; railroad beds; utility rights-of-way, and ditches (USFWS 1990). Plant species associated with Knieskern's beaked-rush include: poverty grass (Aristida longispica), warty panic-grass (Panicum verrucosum), and spatulate-leaved sundew (Drosera intermedia), species characteristic of temporarily inundated mineral soils and open areas (Gordon 1993).

Because Rhynchospora kneiskernii typically occurs within wet openings of pitch-pine forest -- a community type established and maintained by fire -- it may be fire-dependent (USFWS 1993). Because fires are now suppressed in much of its habitat, the future of the species and these types of communities is uncertain.

  Rhynchospora kneiskernii is known only from New Jersey in Atlantic, Burlington, Camden, Monmouth, and Ocean Counties in the heart of the Pinelands. Populations were previously known from Camden County, New Jersey, but no longer occur there (USFWS 1991). Two collections were made from Sussex County in Delaware; however, the species has not been observed there since 1875, despite a decade of concerted searches on the part of botanists in appropriate habitat (USFWS 1993, NatureServe 2001). Thus, the species is presumed extirpated in Delaware.

Number Left
  38 extant populations of Rhynchospora kneiskernii are reported in New Jersey (USFWS 1993). An additional 14 occurrences are considered historic. Population sizes vary from a dozen or so culms to groups covering two acres, and plant numbers vary dramatically year to year, especially as water levels fluctuate in the wetlands they inhabit (USFWS 1991). Thus, the total population level of Rhynchospora kneiskernii is extremely difficult to estimate.


Global Rank:  
Guide to Global Ranks
Federal Status:  
Guide to Federal Status
Recovery Plan:  

State/Area Protection
  State/Area Rank Status Date  
  Delaware SX 12/14/2001  
  New Jersey S1 E 9/1/2001  

Conservation, Ecology & Research

Ecological Relationships
  Despite interest in its rarity, ecological interactions of this species with other plants and animals do not appear to have been studied (or published in the scientific literature).

Rhynchospora kneiskernii behaves as an annual or a short-lived perennial (U. S. Fish and Wildlife Service 1997). Therefore, its population numbers can fluctuate greatly from year to year.

The plant is a wetland obligate (USDA 2001) and highly intolerant of drought; populations crashed in 1985, a very dry year (USFWS 1991). It thrives best in groundwater-controlled wetlands that undergo period changes in water level, where other plant species are sparse.

This species may benefit from fire, which can revert a wetland to an early successional state and simultaneously provide a flush of carbon and nutrients to otherwise infertile soils.

The U. S. Fish and Wildlife Service (USFWS 1991) reports that pathogens and herbivores are not known to attack Rhynchospora kneiskernii. Foliar silica is produced in a variety of Rhynchospora species and other monocots, and may inhibit browsing by animals.

With small, inconspicuous flowers, the species is likely wind-pollinated. The inflated achenes may be water-dispersed, but this has yet to be substantiated.

  As identified by U. S. Fish and Wildlife Service 1991 & 1993, threats include:

Any activities that threaten wetland habitat, hydrology, and water quality in the Pinelands, including: land development, water diversion, road-building, sewage disposal, land-fill creation, and agricultural expansion
Natural succession to shrub or forested wetland, especially if hastened by lowered water table or not arrested by fire
Intensive off-road vehicle use
The location of a majority of all populations on private property, where illegal collecting is difficult to control

Current Research Summary
  The New England Wild Flower Society (Framingham, Massachusetts), has conducted seed germination trials on this species. Moist, cold stratification enhances germination. Seed sown after collection in 1991 germinated and produced plants. These plants flowered in two consecutive years, confirming that the plant can be a short-lived perennial. Seed dried and stored under seed bank conditions for four years between 1991 and 1995 germinated successfully in 1995, demonstrating that the species is capable of seed-banking.

Current Management Summary
  According to the U. S. Fish and Wildlife Service (1991, 1993), conservation and management of R. knieskernii involves integrated site protection and habitat manipulation to maintain early plant succession. Protection efforts focus on reducing known threats to plants, land acquisition, landowner agreements, and management of habitats to maintain conditions conducive to the species establishment and maintenance.

The U. S. Fish and Wildlife Service has also established agreements with the U. S. Department of the Navy, Federal Aviation Administration, and the New Jersey Division of Fish, Game and Wildlife to protect known occurrences of Rhynchospora kneiskernii (USFWS 1993).

Research Management Needs
  Quantification of demography and reproduction, especially in small and marginal populations, to inform a systematic population viability analysis
Studies of seed bank dynamics, seed viability, dispersal, and seedling establishment to determine how new populations are initiated and the optimal habitat conditions for plant growth
Controlled burns of selected areas (with appropriate experimental controls) to assess the role of fire in maintaining populations

Ex Situ Needs
  Methods for ex situ cultivation appear to be relatively well-established for this taxon.


Books (Single Authors)

1988. Protecting the New Jersey Pinelands : A New Direction in Land-Use Management. Piscataway, NJ: Rutgers University Press. 344p.

1998. Pine Barrens: Ecosystem and Landscape. Piscataway, NJ: Rutgers University Press. 684p.

Boyd, H.P. 1991. A Field Guide to the Pine Barrens of New Jersey : Its Flora Fauna Ecology and Historic Sites. Medford, NJ: Plexus Publishing, Inc. 423p.

Gleason, H.A. 1952. The New Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. New York, NY: Hafner Press. 1732p.

Gleason, H.A.; Cronquist, A. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Bronx: The New York Botanical Garden.

Harshberger, J.W. 1989. The Vegetation of the New Jersey Pine Barrens. New York City: Dover Publications, Inc. 329p.

Hough, M.Y. 1983. New Jersey wild plants. Harmony, NJ: Harmony Press. 414p.

Mason, R.J. 1992. Contested Lands : Conflict and Compromise in New Jersey's Pine Barrens (Conflicts in Urban and Regional Development). Philadelphia, PA: Temple University Press.

Stone, W. 1973. The Plants of Southern New Jersey. Boston, Massachusetts: Quarterman Publications, Inc. 828p.

Electronic Sources

USDA. (2002). PLANTS profiles. [Web site] United States Department of Agriculture, Natural Resources Conservation Service. http://www.plants.usda.gov. Accessed: 2002.

USFWS. (1990). Endangered and Threatened Species Accounts. [Web page] U.S. Fish and Wildlife Service, Division of Endangered Species. http://ecos.fws.gov/servlet/TESSSpeciesQuery. Accessed: 2002.

Journal Articles

Carey, J. 1847. A new species of Rhynchospora. The American Journal of Science and Arts. 4: 25.

Davidse, G. 1974. Notes on Rhynchospora (Cyperaceae). Annals of the Missouri Botanical Garden. 61: 529-530.

Lamont, E.E.; Fitzgerald, J.M. 2000. Noteworthy plants reported from the Torrey Range - 2000. Journal of the Torrey Botanical Society. 128

Sorrie, B.A.; Weakley, A.S. 2001. Coastal plain vascular plant endemics: phytogeographic patterns. Castanea. 66: 50-82.

USFWS. 1976. Proposed Endangered Status for 1700 U.S. Plants. Federal Register. 41: 24523-24572.

USFWS. 1991. Determination of the plant, Rhynchospora knieskernii (Knieskern's beaked-rush), to be a Threatened Species. Federal Register. 56: 32978-?.


Commission, Pinelands. 1980. Comprehensive Management Plan for the Pinelands National Reserve and Pinelands Area. New Lisbon, New Jersey, USA: Pinelands Commission. p.439.

Gordon, T. 1993. Monitoring and Survey of Rhynchospora knieskernii in New Jersey. Trenton, New Jersey: New Jersey Office of Natural Lands Management.

Knieskern, P.D. 1857. Catalogue of Plants Growing without Cultivation in Monmouth and Ocean Counties, New Jersey. Trenton, New Jersey: True American Office. p.41.

Radis, R. 1995. Monitoring and survey research on Rhynchospora knieskernii Carey in New Jersey. Trenton, New Jersey: New Jersey Office of Natural Lands Management. p.16.

Rawinski, T.; Cassin, J. 1986. Status of Rhynchospora knieskernii. Newton Corner, Massachusetts: U.S. Fish and Wildlife Service. p.4. Unpublished Report.

Robichaud, B. 1980. A Conceptual Framework for Pinelands Decision Making. New Brunswick, New Jersey: Center for Coastal and Environmental Studies, Rutgers University. p.78.

Roman, C.; Good, R. 1983. Pinelands Wetlands: Values, Function, and Man's Impacts. Center for Coastal and Environmental Studies. Rutgers University: New Brunswick, New Jersey. p.106.

Stone, W. 1911. The Plants of Southern New Jersey with special reference to the flora of the pine barrens. Trenton, New Jersey: New Jersey State Museum. annual report 1910, Part II, 21-828.

USFWS. 1993. Knieskern's Beaked-Rush (Rhynchospora knieskernii) Recovery Plan. Hadley, Massachusetts: U.S. Fish and Wildlife Service. p.40.

  This profile was updated on 3/4/2010
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