Potamogeton ogdenii Stephen M. Young

Potamogeton ogdenii
Stephen M. Young

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
Not Applicable - A state conservation status rank is not applicable because the species is not a suitable target for conservation activities (e.g., species is a hybrid, a domesticated species, not native to New York, an accidental or infrequent visitor outside of its normal range, a transient or migrant just passing through the state, or a species with only unconfirmed or doubtful reports).
Global Conservation Status Rank
Critically Imperiled or Imperiled globally - At very high or high risk of extinction due to rarity or other factors; typically 20 or fewer populations or locations in the world, very few individuals, very restricted range, few remaining acres (or miles of stream), and/or steep declines. More information is needed to assign either G1 or G2.


Did you know?

This pondweed was not described as a separate species until 1983 and honors Dr. Eugene Ogden, former New York State Botanist and pondweed specialist.

State Ranking Justification

There are only three known populations. These populations may be threatened by the use of aquatic herbicides. As more surveys are conducted, new populations may be encountered. With so few populations now known though, this plant will likely remain rare long into the future.

Short-term Trends

As a relatively newly described species, there is not a lot of historical evidence to determine a trend. Based on minimal evidence, populations are presumed stable. There is a possibility that more populations will be discovered in the future.

Long-term Trends

This pondweed was always very rare in New York. As a relatively new species originating from a hybrid cross, there is a chance that this species will be found in new locations as people better understand how to identify it and as the species possibly establishes itself in new areas.

Conservation and Management


Water quality deterioration from increasing shoreline development and the use of herbicides to control invasive aquatic plants could threaten this plant if these activities are not carefully planned. It may also be threatened by lake eutrophication due to runoff from nearby activities.

Conservation Strategies and Management Practices

No direct management is required for this species; however, in areas where recreational activities are also present there should be monitoring efforts to minimize the impact of changes in water quality, motor boats, and the use of aquatic herbicides.

Research Needs

Research is needed to determine how different aquatic herbicides affect this plant.



An aquatic plant of alkaline waters, including slow streams, calcareous ponds, muddy shorelines, and lakes without high horsepower boats (New York Natural Heritage Program 2004). Alkaline waters of ponds and lakes (Flora of North America 2000). Alkaline waters (Gleason and Cronquist 1991).

Associated Ecological Communities

  • Deep emergent marsh* (guide)
    A marsh community flooded by waters that are not subject to violent wave action. Water depths can range from 6 in to 6.6 ft (15 cm to 2 m). Water levels may fluctuate seasonally, but the substrate is rarely dry, and there is usually standing water in the fall. * probable association but not confirmed.
  • Eutrophic dimictic lake*
    The aquatic community of a nutrient-rich lake that occurs in a broad, shallow basin. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall); they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter. * probable association but not confirmed.
  • Farm pond/artificial pond*
    The aquatic community of a small pond constructed on agricultural or residential property. These ponds are often eutrophic, and may be stocked with panfish such as bluegill and yellow perch. * probable association but not confirmed.
  • Marl pond* (guide)
    The aquatic community of a small, shallow, spring-fed pond in which the water has a high concentration of calcium. The calcium precipitates out of the water as calcium carbonate and forms a marl sediment. * probable association but not confirmed.
  • 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. * probable association but not confirmed.
  • Mesotrophic dimictic lake
    The aquatic community of a lake that is intermediate between an oligotrophic lake and a eutrophic lake. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall); they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter.

Associated Species

  • Chara vulgaris
  • Elodea canadensis (Canada waterweed)
  • Fissidens spp.
  • Nymphaea odorata ssp. Tuberosa
  • Potamogeton illinoensis (Illinois pondweed)
  • Potamogeton spp.
  • Stuckenia pectinata (Sago pondweed)
  • Utricularia spp.


New York State Distribution

This aquatic plant is limited to the alkaline waters near the foothills of the Taconic Ridge and disjunct to at least one local population in central New York (Oswego County). More survey work should be conducted in the alkaline waters of eastern New York, Oswego County, and the Finger Lakes region.

Global Distribution

This aquatic plant has a very limited distribution. It is only known from Massachusetts, Vermont, and New York.

Identification Comments

General Description

This is an aquatic plant with masses of long, very narrow leaves visible just below the surface of waters with a high pH. There are three, sometimes five veins running the length of the leaf. There are one or two rows of large open cells on either side of the mid-vein and often, but not always, a little bristle at the tip of the leaf. It is often in fruit with small clusters of fruits at the end of short arching stalks. The fruits are large for a pondweed .

Identifying Characteristics

This pondweed has a stem that is round or only slightly flattened. All leaves are submersed and 1-3 mm broad with 5-11 (3-13) veins. The peduncles are mostly terminal. Winter buds are uncommon but when present these are stiff with the outer flat leaves ascending or with inner and outer leaves occasionally undifferentiated. The stipules are brown (rarely white) and fibrous only at the tips. There are 2-4 (0-6) lacunae bands per leaf.

Best Life Stage for Proper Identification

This plant can be identified vegetatively. If found, vegetative material with submerged leaves and stipules should be nicely pressed. This will allow for easier verification later.

Similar Species

Odgen's pondweed (Potamogeton ogdenii) is a species of hybrid origin between Hill's pondweed (Potamogeton hillii) and flat-stemmed pondweed (Potamogeton zosteriformis). Subsequently, it has characteristics resembling both. Potamogeton hillii has 3 (-5) veins, the diameter of the nodal gland is 0.1-0.3 mm or absent, the peduncles are mostly axillary and 6-14 mm long, and the spike is globose and 4-7 mm long. Potamogeton zosteriformis has submersed leaves with 15-35 veins, is 2 or more mm wide, and is stem flattened. The closely related hybrid Potamogeton x longiligulatus (a hybrid between Potamogeton strictifolius and Potamogeton zosteriformis) has 5-18 veins, the diameter of the nodal gland is 0.1-0.4 mm or absent, the peduncles are mostly terminal and 15-30 mm long, the spike is cylindrical and 10-35 mm long, and it rarely fruits (fruits have only been observed once).

Best Time to See

Vegetative plants can be seen from early July to mid-September. This pondweed rarely sets fruit. Surveys are best conducted between July and early September.

  • Vegetative

The time of year you would expect to find Ogden's Pondweed vegetative in New York.

Ogden's Pondweed Images


Ogden's Pondweed
Potamogeton x ogdenii Hellquist & R.L. Hilton

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


  • Potamogeton hillii x zosteriformis

Comments on the Classification

This pondweed is possibly a hybrid between Potomogenon hillii and Potomogenon zosteriformis but it is rarely found with both its parents. Once established, it does appear to produce fertile fruit.

Additional Resources

Best Identification Reference

Crow, Garrett E. and C. Barre Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America: A revised and enlarged edition of Norman C. Fassett's a Manual of Aquatic Plants. Volume One: Pteridophytes, Gymnosperms, and Angiosperms: Dicotyledons. The University of Wisconsin Press. Madison, Wisconsin. 536 Pages.

Other References

Flora of North America Editorial Committee. 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.

Gleason, H.A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. New York Botanical Garden, Bronx, New York. 910 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.

Hellquist, C.B. and T. Mertinooke-Jongkind. 2003. Ogden's Pondweed (Potamogeton ogdenii) Conservation and Research Plan for New England. New England Wild Flower Society, Framingham, Massachusetts, USA. Available at http://www.newfs.org/conserve/pdf/Potamogetonogdenii.pdf. 16 pp.

Hellquist, C.B., and R.L. Hilton. 1983. A new species of Potamogeton (Potamogetonaceae) from northeastern U.S. Systematic Botany 8(1): 86-92.

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. 2020. New York Natural Heritage Program Databases. Albany, NY.

Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.

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 http://www.fccdr.usf.edu/. University of South Florida http://www.usf.edu/]. New York Flora Association http://newyork.plantatlas.usf.edu/, Albany, New York

Werier, David. 2017. Catalogue of the vascular plants of New York State. Memoirs of the Torrey Botanical Society. Volume 27. The Torrey Botanical Society. The New York Botanical Society, Bronx, NY 10458. 542 pages.


About This Guide

Information for this guide was last updated on: February 15, 2005

Please cite this page as:
New York Natural Heritage Program. 2020. Online Conservation Guide for Potamogeton x ogdenii. Available from: https://guides.nynhp.org/ogdens-pondweed/. Accessed April 3, 2020.

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