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Kevin Doyle

Prairie Milkweed (Asclepias sullivantii)

Life history

Species overview

Prairie Milkweed (Asclepias sullivantii), a Wisconsin Threatened plant, is found in moist prairies. Blooming occurs early June through early July; fruiting occurs throughout July. The optimal identification period for this species is early June through early July.

Synonyms: None


  • Distinguishing characteristics: Distinguished by its leaves, which are glabrous, sessile and erect or ascending on main stem, but do not have wavy margins.
  • Flower characteristics: Two or more flower heads extend from the upper stem; flowers purplish-rose colored with 9 to 12 mm long lobes and 5 mm long hoods.
  • Fruit characteristics: Pods hairless and may be covered in wart-like bump, bent abruptly downward.
  • Leaf characteristics: Thick, hairless, broadly elliptic to ovate to oblong, 10 to 15 cm in length, sessile (connect directly to stem without petiole) and usually erect and ascending.


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


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Andropogon gerardii, Aster ericoides, Eryngium yuccifolium, Petalostemum purpureum, Silphium species, Solidago rigida, Liatris aspera, Veronicastrum virginicum.

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 Prairie Milkweed (Asclepias sullivantii). 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 Asclepias sullivantii in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS2S3
Global RankG5
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 moist prairies.
  • Soils: Moist to mesic, rich soils.

Natural communities

This table lists the natural communities that are associated with Prairie Milkweed. 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
Wet-mesic Prairie 3
Mesic Prairie 2

Ecological landscapes

This table lists the ecological landscape association scores for Prairie Milkweed. 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 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

  • Prescribed burns and/or brushing may be beneficial (dependent on local site conditions).
  • Maintain and restore open habitat through selective clearing and brushing.


Prairie Milkweed Photo.

Photo © William S. Alverson.

Prairie Milkweed Photo.

Asclepias sullivantii.

Photo by Thomas Meyer, Wisconsin DNR.

Prairie Milkweed Photo.

Prairie milkeed occurs almost exclusively in good quality wet-mesic prairie remnants. More populations of this prairie obligate are known from the Southeast Glacial Plains than any other Ecological Landscape.

Photo by Thomas Meyer, Wisconsin DNR.

Prairie Milkweed Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Prairie Milkweed Photo.

Photo © William S. Alverson.

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