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Hill's Pondweed (Potamogeton hillii)

Life history

Species overview

Hill's Pondweed (Potamogeton hillii), a Wisconsin Special Concern plant, is found in clear, cold, alkaline water in small, slow-flowing streams, ponds with a muddy substrate. Fruiting occurs late July through August. The optimal identification period for this species is mid-July through late August.

Synonyms: Potamogeton porteri


  • Distinguishing characteristics: Fruit rounded on the sides and with 3 low, ridge-like keels; rhizome undeveloped.
  • Flower characteristics: Spike head-like, 4 to 7 mm, with 1 or 2 whorls of flowers.
  • Fruit characteristics: Body obovate, flattened, 2.5 to 4 mm, with a low, sharp dorsal keel and a pair of lateral keels; beak approximately 0.5 mm.
  • Leaf characteristics: Submersed, narrowly linear, 3 to 7 cm long by 1 to 2 mm wide, usually sharply acute or tipped with a short, sharp, abrupt point; leaf veins 3 to 5, the lateral veins very delicate, the midvein flanked by one or two rows of lacunar cells on each side; stipular sheaths axillary, free, white or light brown, 1 to 1.5 cm, becoming fibrous.


  • Blooming phenology:
  • Fruiting phenology: late July through August
  • Optimum time to identify: The optimal identification period for this species is mid-July through late August


  • Growth form: Aquatic forb-submergent
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Not recorded for Wisconsin specimens.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - state and federal - and the rank (S and G Ranks) for Hill's Pondweed (Potamogeton hillii). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.

Documented locations of Potamogeton hillii in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS1
Global RankG3
Tracked by NHIY

Habitats and landscapes

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

General habitat information

  • Habitat description: Found in clear, cold, alkaline water in small, slow-flowing streams, ponds with a muddy substrate.
  • Soils: Alkaline soils.

Natural communities

This table lists the natural communities that are associated with Hill's Pondweed. Scores for natural community associations are: "significant" association (score=3), "moderate association" (score=2) or the species can be present but is only weakly associated with the community (score=1).

Natural communities score
Coolwater streams 3
Submergent Marsh 3

Ecological landscapes

This table lists the ecological landscape association scores for Hill's Pondweed. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

Ecological landscape score
North Central Forest 3

Species guidance

The Endangered Resources Program has developed avoidance measures and management guidelines for plants on the Natural Heritage Working List. These are a work in progress, and we welcome your suggestions and feedback. Sources used in developing this information can be found here.

Avoidance measures

These are specific actions designed to avoid "take" (mortality) of this species.

  • Avoid known individual plant locations and conduct operations elsewhere when they are least likely to cause damage. Ideally, this would involve frozen, snow-covered ground. However, in areas of the state where frozen conditions are unreliable, very dry soils late in the growing season might be the best available alternative. Consult with a biologist, if needed.
  • Avoid broadcast spraying of herbicides; use care with spot spraying.

Management guidance

Management guidelines are additional considerations that may help maintain or enhance habitat for this species

  • This species is likely sensitive to water quality. Following BMPs around streams and buffering associated drainages will reduce eutrophication and prevent water quality degradation.


Hill's Pondweed Photo.

Photo ©  Voss.

Hill's Pondweed Photo.

Photo ©  Voss.

Support for Wisconsin's rare plant information has been provided by the Division of Forestry, the Endangered Resources Fund and the Wisconsin Rare Plant Preservation Fund. To donate, visit the Natural Resources Foundation of Wisconsin [exit DNR].

Last revised: Wednesday, May 05, 2021
Southwest Savanna Southern Lake Michigan Coastal Western Coulees and Ridges Southeast Glacial Plains Central Sand Hills Central Lake Michigan Coastal Central Sand Plains Northern Lake Michigan Coastal Northern Lake Michigan Coastal Northeast Sands Western Prairie North Central Forest Northern Highlands Northwest Lowlands Northwest Sands Northwest Lowlands Superior Coastal Plains Forest Transition