Ambiguous Spike Rush

Eleocharis ambigens Fern.

Eleocharis fallax
Richard Ring

Monocotyledoneae (Monocots)
Cyperaceae (Sedge Family)
State Protection
Listed as Endangered by New York State: in imminent danger of extirpation in New York. For animals, taking, importation, transportation, or possession is prohibited, except under license or permit. For plants, removal or damage without the consent of the landowner is prohibited.
Federal Protection
Not Listed
State Conservation Status Rank
Critically Imperiled in New York - Especially vulnerable to disappearing from New York due to extreme rarity or other factors; typically 5 or fewer populations or locations in New York, very few individuals, very restricted range, very few remaining acres (or miles of stream), and/or very steep declines.
Global Conservation Status Rank
Apparently or Demonstrably Secure globally - Uncommon to common in the world, but not rare; usually widespread, but may be rare in some parts of its range; possibly some cause for long-term concern due to declines or other factors. More information is needed to assign either G4 or G5.


Did you know?

The species name fallax is Latin for deceitful or deceptive and its common name in some states is deceitful spike-rush. This refers to its close relationship to other similar species and the difficulty of telling them apart (Flora of North America Editorial Committee 2002). Another of its common names, creeping spike-rush, is also used for the more common Eleocharis palustris.

State Ranking Justification

There are 2 existing very small populations which may be threatened by Phragmites and overuse of the surrounding wetlands. There are four occurrences from the early 1900s which have not been rediscovered.

Short-term Trends

Follow-up surveys have not been done to gather data about short-term trends.

Long-term Trends

This plant has always been very rare in New York but not enough data has been gathered to understand long-term trends.

Conservation and Management


Phragmites is a threat in the marshes where this occurs.

Conservation Strategies and Management Practices

Control Phragmites invasions in the salt marshes where it exists and prevent new incursions. Natural buffers should be established around the salt marshes to decrease pollution runoff and other direct human disturbances.

Research Needs

This species has had a confusing taxonomic history and herbarium specimens of all closely-related species should be examined to determine if more populations exist. Research could also be done to help augment existing populations.



Only two New York sites with Eleocharis fallax have been described; one was an artificial, weedy wetland adjacent to a wastewater treatment plant, and the other an open wetland adjacent to small pond. More information on the habitat requirements of Creeping Spikerush in New York is needed (New York Natural Heritage Program 2010). Fresh to brackish pond and lakeshores, marshes (FNA 2002). Fresh and brackish swamps along the coast (Gleason and Cronquist 1991).

Associated Ecological Communities

  • Coastal plain pond* (guide)
    The aquatic community of the permanently flooded portion of a coastal plain pond with seasonally, and annually fluctuating water levels. These are shallow, groundwater-fed ponds that occur in kettle-holes or shallow depressions in the outwash plains south of the terminal moraines of Long Island, and New England. A series of coastal plain ponds are often hydrologically connected, either by groundwater, or sometimes by surface flow in a small coastal plain stream.
  • Coastal plain pond shore* (guide)
    The gently sloping shore of a coastal plain pond with seasonally and annually fluctuating water levels. Plants growing on the pond shore vary with water levels. In dry years when water levels are low there is often a dense growth of annual sedges, grasses, and herbs. Submerged and floating-leaved aquatic plants, such as fragrant waterlily and pondweeds, may become "stranded" on the exposed shore. In wet years when the water level is high only a few emergents and floating-leaved aquatics may be noticeable. T
  • Sewage treatment pond*
    The aquatic community of an artificial pond constructed for sewage treatment (chemical and biological decomposition of sewage) prior to release to a stream or aquifer.

* probable association but not confirmed.


New York State Distribution

This spikerush is currently known only from Suffolk County on Long Island with one historical record from the Bronx and one from Ulster County.

Global Distribution

This spikerush is most common on the coastal plain in New Jersey and Delmarva Peninsula with scattered populations south to Florida and Alabama. It extends to the west to Louisiana and a couple of counties in eastern Texas where it is rare. There are a few rare populations in southeastern New York and southern New England.

Identification Comments

General Description

Spikerushes consist of a simple stem (the leaves bladeless and inconspicuous), with the infloresence consisting of a solitary, many-scaled spikelet at the top of the stem. The perianth (sepals and petals), if present, is reduced to bristles. The base of the style is expanded into a tubercle, and is usually persistent on the fruit (achenes). Eleocharis fallax is a perennial, mat-forming species with long rhizomes. The stems are round (often ridged in dry specimens), and 30 to 75 cm tall, with purplish bases. The leaf-sheaths are persistent with obtuse, firm, red tips. The spikelets are egg-shaped to rounded and 5 to 12 mm tall, and the floral scales are deciduous. There are 1 to 5, brown, stout, perianth bristles, unequal in length but none exceeding the achene. The achenes are either compressed 3-sided or thickly biconvex, with evident angles, and have an evidently pitted surface. The tubercles are whitish-brown, pyramid-shaped, and not depressed. (FNA 2002, Gleason and Cronquist 1991)

Best Life Stage for Proper Identification

Specimens with complete stems and mature, intact fruits are needed for identification.

Best Time to See

Creeping Spikerush's fruits mature in July and persist into October.

  • Fruiting

The time of year you would expect to find Ambiguous Spike Rush fruiting in New York.

Ambiguous Spike Rush Images


Ambiguous Spike Rush
Eleocharis ambigens Fern.

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Monocotyledoneae (Monocots)
        • Order Cyperales
          • Family Cyperaceae (Sedge Family)

Additional Common Names

  • Creeping Spike Rush
  • Spikerush


  • Eleocharis fallax Weatherby

Additional Resources


Fernald, M. L. 1950. Gray's manual of botany. 8th edition. Corrected printing (1970). D. Van Nostrand Company, New York. 1632 pp.

Flora of North America Editorial Committee. 2002. Flora of North America, North of Mexico. Volume 23. Magnoliophyta: Commelinidae (in part): Cyperaceae. Oxford University Press, New York. 608 pp.

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

Mitchell, Richard S. and Gordon C. Tucker. 1997. Revised Checklist of New York State Plants. Contributions to a Flora of New York State. Checklist IV. Bulletin No. 490. New York State Museum. Albany, NY. 400 pp.

New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

New York Natural Heritage Program. 2024. New York Natural Heritage Program Databases. Albany, NY.

Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research University of South Florida]. New York Flora Association, Albany, New York


About This Guide

This guide was authored by: Stephen M. Young and Richard M. Ring

Information for this guide was last updated on: January 26, 2012

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Eleocharis ambigens. Available from: Accessed April 16, 2024.