American Shoreweed (Littorella uniflora)

Life history

Species overview

American Shoreweed (Littorella uniflora), a Wisconsin Special Concern plant, is found in shallow to deep water of very soft, clear, oligotrophic lakes, usually with a sandy bottom. Blooming occurs throughout July; fruiting occurs late July through late August. The optimal identification period for this species is late July through late August.

Synonyms: Littorella americana, Littorella uniflora var. americana

Identification

• Distinguishing characteristics: Distinguished from other small, linear-leaved aquatics simply by its round leaves, which have only 1 vein. Other small linear-leaved aquatic species have either bulbous leaf bases (Isoetes), triangular leaves (Eriocaulon), flat leaves (Juncus pelocarpus, Sagittaria and Valisneria) or stolons connecting clumps (Ranunculus flammula).
• Flower characteristics: Unisexual, basal, in groups of 3; sepals 2.5 to 4 mm long, lanceolate.
• Fruit characteristics: Cylindric achenes, 2 mm long and half as wide.
• Leaf characteristics: Linear, terete, glabrous to 5 cm.

Phenology

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

Other

• Growth form: Aquatic forb-emergent
• Vegetative reproduction:
• Life cycle: Perennial
• Comments: Associated Species: Lobelia dortmanna, Myriophyllum tenellum. Elatine minima, Isoetes spp., Eriocaulon septangulare, Gratiola aurea.

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 American Shoreweed (Littorella uniflora). 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.

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 shallow to deep water of very soft, clear, oligotrophic lakes, usually with a sandy bottom.
• Soils: Wet, sandy soils.

Natural communities

This table lists the natural communities that are associated with American Shoreweed. 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).

Ecological landscapes

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

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 broadcast spraying of herbicides; use care with spot spraying.
• 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.

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.
• Minimize disturbance to hydrology, including soil disturbance from rutting.

Other resources

Links to additional American Shoreweed information

Other links related to vascular plants (all exit the DNR website)

• Wisconsin Flora
• NatureServe Explorer
• Atlas of Wisconsin Prairie and Savanna Flora - Wisconsin State Herbarium
• USDA - NRCS Plants Database
• USGS Midwestern Wetland Flora - field office guide to plant species
• eFloras
• Cofrin Center for Biodiversity Herbarium
• Intermountain Herbarium Grasses of North America
• Orchids of Wisconsin

Photos

Click to view a larger version. Please considering donating a photo to the Natural Heritage Conservation Program for educational uses. Photo use