Slender Pondweed

Stuckenia filiformis ssp. alpina (Blytt) Haynes, D.H. Les, & M. Kral

Stuckenia filiformis ssp. alpina
Ben Legler

Monocotyledoneae (Monocots)
Potamogetonaceae (Pondweed 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
Secure globally - Both the species as a whole and the subspecies/variety are common in the world; widespread and abundant (but may be rare in some parts of its range).


Did you know?

The genus was named by Carl Borner (1880-1953), a German entomologist from Bremen, for Wilhelm Adolf Stucken (1860-1901), headmaster of the Gottingen Gymnasium and amateur botanist associated with the Bremen herbarium (Flora of Wisconsin website, Wikipedia contributors). The species name refers to its very narrow leaves and the subspecies to its northern distribution although it occurs farther to the south than the subspecies filiformis which only occurs in northern Canada, Alaska, and Greenland (Flora of North America 2000).

State Ranking Justification

There are 2 verified occurrences,  about 15 historical occurrences of spp. alpina, and 1 verified occurrence and 5 historical occurrences of ssp. occidentalis. The subspecies are being combined into Stuckenia filiformis (Werier 2015).

Short-term Trends

The short term trend may be a decline but remains unknown because only three populations are extant as of 1988, and precise counts have not been made during recent surveys. An additional historical population may have disappeared as it could not be relocated during the most recent survey in 1998. Resurveys with population counts are needed to establish a baseline for trend assessment.

Long-term Trends

The long term trend appears to be a significant decline in populations. One population has been extirpated,  three populations have been confirmed as extant but lack specific counts, and the remaining 20 historical records (from 1940's or earlier) have not been resurveyed.

Conservation and Management


Destruction by the removal or chemical treatment of aquatic vegetation from lakes could threaten populations of this species occurring in managed lakes.

Conservation Strategies and Management Practices

Protect populations occuring in lakes from destruction by aquatic vegetation management activities.

Research Needs

Studies to determine the specific habitat preferences of the species in New York are needed.



In New York, the only two extant ppulations have been found in high pH settings including a small marl-bottomed stream with the alga species Chara, and in an aquatic bed in shallow water of an alkaline lake. Historical collections of this plant has been made from swiftly running water and shallow channels of large rivers, washed up on sandy inland lake beaches, in cold brooks, and in crevices in metamorhpic rock in a lake (New York Natural Heritage 2015). Shallow, still or slow-moving, circumneutral to basic water of lakes and rivers.(Go Botany 2015). Calcareous, saline, or brackish shallow to deep waters of standing waters ponds and lakes, cold slow to fast moving streams and rivers, ditches, and coastal inshore waters at elevations from 0--3280 m (FNA 2000).

Associated Ecological Communities

  • Deepwater river
    The aquatic community of very large, very deep, quiet, base level sections of streams with a very low gradient. In places the water is deep enough so that light cannot reach the river bottom.
  • Marsh headwater stream (guide)
    The aquatic community of a small, marshy perennial brook with a very low gradient, slow flow rate, and cool to warm water that flows through a marsh, fen, or swamp where a stream system originates. These streams usually have clearly distinguished meanders (i.e., high sinuosity) and are in unconfined landscapes.
  • Sand beach*
    A sparsely vegetated community that occurs on unstable sandy shores of large freshwater lakes, where the shore is formed and continually modified by wave action and wind erosion. Characteristic species that are usually present at very low percent cover include various grasses and other herbs.
  • Summer-stratified monomictic lake (guide)
    The aquatic community of a lake that is so deep (or large) that it has only one period of mixing or turnover each year (monomictic), and one period of stratification. These lakes generally do not freeze over in winter (except in unusually cold years) or form only a thin or sporadic ice cover during the coldest parts of midwinter, so the water circulates and is isothermal during the winter.

* probable association but not confirmed.

Associated Species

  • Chara vulgaris


New York State Distribution

In New York, Slender Pondweed is found in central and western NY, as well as in Jefferson and St. Lawrence Counties.

Global Distribution

This is a circumboreal species ranging from Greenland west to Alaska and south to California, Arizona, New Mexico and Nebraska in the west. From Minnesota its U.S. range extends east through the upper midwestern states Wisconsin and Michigan up through New York and the northern New England state and from New Brunswik and Nova Scotia to New Foundland. It is considered possibly extirpated from Ohio, Pennsylvania and New Hampshire.

Identification Comments

Identifying Characteristics

This plant is an aquatic plant that grows with its narrow-linear (0.2-1.5mm wide), alternate leaves completely submersed. Its leaves have closed stipular sheaths and are typically blunt to obtuse at the apex, but sometimes with a shallow central notch (retuse) or rarely ending in a small distinct point (apiculate). The leaves are cross-septate throughout.  The flowering spikes are submersed or sometimes floating and bear well-separated lower whorls of flowers on thin, flexuous peduncles.The floral stigma are broad, sessile, and do not form a beak on the mature fruits (drupes).  The drupes are uncompressed and 2-3mm long (GoBotany 2015).

Best Life Stage for Proper Identification

The entire plant with leaves, mature fruiting stems and intact fruit are needed for positive identification.

Similar Species

In New York, the only other Stuckenia species is S. pectinata which can be distinguished from S filifrmis by its open stipular sheaths with overlapping edges vs. closed sheaths, leaf blades that are commonly acute at the apex vs. typically blunt or obtuse in S filiformis, and stigmas borne on a short style persisting on the mature fruit (drupes) as a tiny beak vs. stigmas sessile and not forming a beak. S pectinata's drupes are 3-4.5 mm long, vs. 2-3 mm long drupes in S. filiformis. Plants from the genus Potamogeton with narrow submerged leaves may be confused with Stuckenia filiformis, but they can be distinguished by the presence of floating leaves (if they occur), leaf blades that are cross-septate only on their central lacunar bands, stipules distinct from the blade or typically fused for less than 10 mm (vs. typically 10 - 30 mm in Stuckenias), and mature drupes compressed with a distinctly coiled embryo.

Best Time to See

The leaves of this species typically appear in late July and persist through early October. Fruiting generally begins in early August and continues through early September. (fruit mid-August -mid-October for ssp. occidentalis

  • Vegetative
  • Fruiting

The time of year you would expect to find Slender Pondweed vegetative and fruiting in New York.

Slender Pondweed Images


Slender Pondweed
Stuckenia filiformis ssp. alpina (Blytt) Haynes, D.H. Les, & M. Kral

  • Kingdom Plantae
    • Phylum Anthophyta
      • Class Monocotyledoneae (Monocots)
        • Order Najadales
          • Family Potamogetonaceae (Pondweed Family)

Additional Common Names

  • Pondweed


  • Coleogeton filiformis ssp. alpinus (Blytt) D. H. Les. & Haynes
  • Potamogeton filiformis var. alpinus (Blytt) Aschers. & Graebn.
  • Potamogeton filiformis var. borealis (Raf.) St. John
  • Potamogeton filiformis var. macounii Morong

Additional Resources


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.

House, Homer D. 1924. Annotated list of the ferns and flowering plants of New York State. New York State Museum Bulletin 254:1-758.

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. 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

Werier, David. 2015 Provisional New York Staet Vascular Plant Checklist. Botanical and Ecological Consulting. New York Natural Heritage Program. Willseyville, New York.


About This Guide

Information for this guide was last updated on: January 7, 2016

Please cite this page as:
New York Natural Heritage Program. 2024. Online Conservation Guide for Stuckenia filiformis ssp. alpina. Available from: Accessed May 26, 2024.