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Dwarf Lake Iris (Iris lacustris)

Life history

Species overview

Dwarf Lake Iris (Iris lacustris), a Wisconsin Threatened and Federal Threatened plant, is found near Lake Michigan on beach ridges, stabilized dunes, limestone ridges, forest gaps and edges, and ditches. Blooming occurs early May through early July; fruiting occurs late June through late July. The optimal identification period for this species is late May through early July.

Synonyms: Iris cristata ssp. lacustris, Iris cristata var. lacustris


  • Distinguishing characteristics: Plants much shorter in stature (less then 15 cm vs. 50 to 100 cm) than other Iris species in our region.
  • Flower characteristics: Flowers 5 to 6 cm wide, violet; perianth tube dull yellow, 1 to 2 cm, dilated upwards, shorter than the sepals and petalsl; petals notched at the apex.
  • Fruit characteristics: Seeds dark brown, with an aril (fleshy thickening of seed coat).
  • Leaf characteristics: Broadly linear, curved-arching, 4 to 6 cm at anthesis, later 15 cm long by 5 to 10 mm wide.


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


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Thuja occidentalis, Abies balsamea, Zigadenus glaucus, Carex eburnea, Cornus canadensis, Juniperus communis, Shepherdia canadensis, Polygala pauciflora, Arctostaphylos uva-ursi.

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 Dwarf Lake Iris (Iris lacustris). 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 Iris lacustris in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in WisconsinLT
State RankS3
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 near Lake Michigan on beach ridges, stabilized dunes, limestone ridges, forest gaps and edges, and ditches.
  • Soils: Gravelly, calcareous soils.

Natural communities

This table lists the natural communities that are associated with Dwarf Lake Iris. 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 Dwarf Lake Iris. The scores (3=High, 2=Moderate, 1=Low, 0=None) also correspond to the map.

Map of the Ecological Landscapes of Wisconsin.

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 site preparation that heavily disturbs herbaceous ground layer and soil; these include bulldozing and furrowing, as well as grubbing and stump removal.
  • Avoid locating landings, staging areas, or access routes on or near known populations.
  • 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

  • Survey for and control invasive plants prior to conducting timber operations, as these can be spread by vehicles and often respond vigorously to increased light; see forestry BMPs for invasive species.
  • Avoid any activities which destabilize the dune, including the use of off-road vehicles, removal of native vegetation and pedestrian recreational overuse.
  • Maintain partial canopy to encourage woodland species; avoid closed-canopy conditions.


Dwarf Lake Iris Photo.

Dwarf lake iris.

Photo by Drew Feldkirchner, Wisconsin DNR.

Dwarf Lake Iris Photo.

Photo by Thomas Meyer, Wisconsin DNR.

Dwarf Lake Iris Photo.

Dwarf lake iris is a Great Lakes endemic restricted in Wisconsin to semi-open, calcareous habitats in a few northeastern counties.

Photo by Thomas Meyer, Wisconsin DNR.

Dwarf Lake Iris Photo.

Photo © J. Hale.

Dwarf Lake Iris Photo.

Dwarf lake iris.

Photo © Len Place.

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