Species Profile

Hill's Pondweed

Scientific Name: Potamogeton hillii
Taxonomy Group: Vascular Plants
Range: Ontario
Last COSEWIC Assessment: May 2005
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern

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Quick Links: | Photo | Description | Distribution and Population | Habitat | Biology | Threats | Protection | National Recovery Program | Documents

Image of Hill's Pondweed

Hill's Pondweed Photo 1
Hill's Pondweed Photo 2



Hill's Pondweed is an entirely submerged aquatic plant, 30 to 60 cm long. Its thin stems, medium green or olive-green in colour, are 0.5 to 1 mm in diameter. The silky-tipped leaves are long and narrow, the same colour as the stems, and are 2 to 6 cm long and 1 to 2.5 mm wide. Flowers are grouped in clusters measuring up to 7 mm in length. The plant's flower clusters (spikes) and brown fruit are held above the water surface on curved stalks. Without looking at the flowers or fruit, it is practically impossible to differentiate this species from other narrow-leaved pondweeds.


Distribution and Population

Hill's Pondweed has been observed in southern Ontario and in the states of Michigan, Wisconsin, Ohio, New York, Pennsylvania, Connecticut, Massachusetts and Vermont. In Canada, Hill’s Pondweed is found on Manitoulin Island and the Bruce Peninsula in southern Ontario. Additional reports come from Elgin County, Wellington County and the Peel Regional Municipality. In 2003, Hill’s Pondweed occupied 20 sites in Canada, representing a very small total area. The abundance of populations was very crudely assessed because this species grows in thick patches of intertwined individuals, making it exceedingly difficult to distinguish their number without destroying them. Based on the four sites where fruit helped to positively identify the species, the Canadian population consists of over 55 000 plants. If identification of individuals suspected of being Hill's Pondweed was correct in all cases, this number could rise to approximately 119 600 plants. The lack of monitoring has resulted in little information on the decline of populations. Given its unremarkable appearance, it is likely that Hill’s Pondweed could be more widespread than is currently reported.



Hill’s Pondweed grows in clear, cold water of slow-moving streams, ditches and ponds with a muddy substrate. In Ontario, these aquatic habitats have hard or alkaline waters, as most of the known sites are associated with a rocky bottom composed of dolomitic limestone. Rarely is the species found in turbid or polluted waters or in fast-moving streams. Hill's Pondweed is often associated with other species of pondweed.



Hill’s Pondweed reproduces sexually by seeds. It also multiplies vegetatively, or asexually, by small winter buds that break off from the plant. These buds, produced in the fall, develop into a new plant in the spring after spending the winter in dormancy. Hill's Pondweed flowers in late July and produces fruit from late August to September. Most species of pondweeds are wind pollinated, while the dispersal of seeds occurs by water or aquatic birds. Winter buds are also dispersed by water, and possibly by birds. Hill’s Pondweed can also occasionally form a rhizome-like structure or underground stem. The newly rooted portions can establish as independent plants. Like other aquatic plants, Hill's Pondweed provides habitat for aquatic invertebrates, food for aquatic birds and mammals, and cover for amphibians and fish. Little information is known about this aquatic species.



The two main potential threats to the Canadian population of Hill’s Pondweed come from destruction of habitat caused by the draining of ponds and wetlands, and poorer water quality due to chemical and thermal pollution. Threats to Hill’s Pondweed can only be speculated on, since few threats have been recorded for most of the known sites in Ontario. One site appeared to be degraded by cattle, but none of the other sites seemed to have any imminent threats. Invasive aquatic plants, such as Curly Pondweed and Reed Canary Grass, may have had an impact on certain populations.



Federal Protection

More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

Hill's Pondweed in the Bruce Peninsula National Park is protected under the Canada National Parks Act. In Ontario, Hill's Pondweed is not protected by any provincial legislation.

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.



PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

9 record(s) found.

COSEWIC Status Reports

COSEWIC Assessments

  • COSEWIC Assessment - Hill's Pondweed (2005)

    Designated Special Concern in April 1986. Status re-examined and confirmed in May 2005. Last assessment based on an update status report.

Response Statements

  • Response Statements - Hill's Pondweed (2005)

    An inconspicuous, rooted, aquatic plant currently known from fewer than 20 Canadian populations and occupying a very small total area of habitat. No imminent limiting factors have been identified that would have significant impacts on this globally rare species, but invasive exotic plants may be impacting some populations.

Action Plans

  • Multi-species Action Plan for Bruce Peninsula National Park and Fathom Five National Marine Park of Canada (2016)

    Bruce Peninsula National Park (BPNP) and Fathom Five National Marine Park (FFNMP) lie at the tip of the Bruce Peninsula which separates Georgian Bay from Lake Huron. The peninsula is 90 km in length and its most prominent feature is the Niagara Escarpment which runs along the entire eastern edge. Within BPNP, the escarpment forms the Georgian Bay shoreline and is recognized as part of the core area of the Niagara Escarpment UNESCO World Biosphere Reserve.  BPNP was established by the federal government in 1987 to protect a representative example of the Great Lakes/St. Lawrence Lowlands natural region. Because of the fragmented nature of the park properties, many of the stresses on the park’s ecosystem originate from outside its boundaries. For this reason, First Nations, local residents, non-governmental organizations, and other groups and land users play an important role in managing, restoring, and protecting the northern Bruce ecosystem. 

Management Plans

  • Management Plan for Hill's Pondweed (Potamogeton hillii) in Canada (2014)

    The Committee on the Status of Endangered Wildlife in Canada designated Hill's Pondweed (Potamogeton hillii) as Special Concern in 1986 and confirmed this status in 2005. The species is listed as Special Concern on the federal Species at Risk Act (SARA). In Ontario, it is listed as Special Concern on the Species at Risk in Ontario (SARO) List under the Endangered Species Act, 2007 (ESA 2007). The global rank of Hill's Pondweed is vulnerable, and it is identified as rare in all nine U.S. states in which it occurs.


COSEWIC Annual Reports

  • COSEWIC Annual Report - 2005 (2005)

    2005 Annual Report to the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.

Consultation Documents

  • Consultation on Amending the List of Species Under the Species At Risk Act: November 2005 (2005)

    The Government of Canada proclaimed the Species at Risk Act (SARA) on June 5, 2003 as part of its strategy for the protection of wildlife species at risk. Attached to the Act is Schedule 1, the list of the species that receive protection under SARA, hereinafter referred to as the 'SARA list'. Canadians are invited to comment on whether all or some of the species included in this document should be added to the SARA list.