Ogden's Pondweed

(Potamogeton x ogdenii)

Status: Endangered (ESA 2009, COSEWIC 2007)

Table of Contents:

Species Identification
Habitat and Biology
Threats/Reasons for Being at Risk
Conservation and Recovery Strategies
How You Can Help

Photo by Jim Bennett: https://www.inaturalist.org/observations/52284026

Species Identification:

Ogden’s Pondweed is an annual, fully submerged aquatic plant species that has very thin, branch-like stems. It has very narrow leaves that are a greenish-brown in colour and are 5-7 cm long. They can occasionally produce fruit in the shape of a spike that is 5-11 mm long. This species can be very hard to distinguish between other Pondweed species and generally grows near these other species.

Habitat and Biology:

This species is considered to be rare globally. It only occurs in the United States at 2 sites in western Connecticut, 3 sites in central New York, 2 sites in central Vermont, and 2 sites in western Massachusetts. In Canada, this species is only found at 2 sites in southeastern Ontario. These sites are located south of Perth at Murphy’s Point Provincial Park and Davis Lock 38 on the Rideau Canal. These sites can be found in the very southeastern part of The Land Between.

Map taken from Government of Canada: https://www.registrelep.gc.ca/virtual_sara/files/cosewic/sr_potamogeton_ogdenii_e.pdf

Photo by Jim Bennett: https://www.inaturalist.org/observations/52284026

Ogden’s Pondweed prefers the clear waters of lakes, ponds, and slow-moving streams. It can also commonly be found with many other Pondweed species, which makes it very hard to distinguish and identify. This species is also thought to prefer hard alkaline water, since both Ontario sites are found by marble bedrock. More research is needed to identify other possible populations, but also other habitat requirements since not much is currently known.

Ogden’s Pondweed reproduces by seeds and the production of winter buds, which are called turions. Fruit can be found in the mid-summer months and turions replace them in the fall. Seeds and winter buds are dispersed by either water or waterfowl.

Threats/ Reasons for being at Risk:

1. Habitat loss: Beaver ponds are a preferred habitat type for Ogden’s Pondweed, but they are becoming less and less available as beavers are persecuted by humans and ponds are drained for development. Other water bodies are also impacted by development, especially shoreline development. Cottagers are also likely to remove aquatic vegetation that grows near their shoreline, and boat propellers commonly shred aquatic vegetation as they pass by.

2. Invasive species: Invasive species like Eurasian water-milfoil and European Frogs-bit, which are commonly found in the same areas as Pondweed and are known to outcompete this species for space and resources.

3. Recreational activities: Shoreline areas are commonly dredged and disturbed to remove aquatic vegetation like Pondweed in order to accommodate recreational activities like swimming, boating, and for aesthetic purposes. Boat traffic can also shred aquatic vegetation and disturb habitats.

Photo by Jim Bennett: https://www.inaturalist.org/observations/52284026

Conservation and recovery strategies:

Not much is known about Ogden’s Pondweed so it is very important to continue vital research on the location, biology, and habitat requirements of this species. The Government of Ontario has plans to continue to locate other areas where this species may be growing- since it grows underwater with other Pondweed species it can be very hard to identify. Where known locations are, further research will be put into place to determine size, habitat, population dynamics, and threats. Habitat is automatically protected where Ogden’s Pondweed is found, and there are plans in place to rehabilitate current and future habitats.

How can you help?

Report any potential sightings of Ogden’s Pondweed to The Land Between’s website, iNaturalist, or the Natural Heritage Information Centre with photos and coordinates.
Stay away from heavily vegetated areas when out on the water with motorized boats.
Keep wetlands natural on your property and avoid using harmful chemicals in these areas.
Volunteer with local organizations, nature clubs, or Provincial parks that participate in surveys or stewardship programs with Species at Risk.

Additional Resources:

Government of Ontario’s Ogden’s Pondweed SAR page
Learn to identify Ogden’s Pondweed and other cool plant species on iNaturalist
New York Natural Heritage Program’s information page

Sources:

Government of Ontario. 2014. Ogden’s Pondweed. Retrieved from: https://www.ontario.ca/page/ogdens-pondweed

COSEWIC. 2007. COSEWIC assessment and status report on the Ogden’s pondweed potamogeton ogdenii in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi. + 19 pp. https://www.registrelep.gc.ca/virtual_sara/files/cosewic/sr_potamogeton_ogdenii_e.pdf