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Kevin Doyle

Green Milkweed (Asclepias hirtella)

Life history

Species overview

Green Milkweed (Asclepias hirtella), a Wisconsin Special Concern plant, is found in wet to dry prairies. Blooming occurs from in June through August. The optimal identification period for this species is in June through August.

Synonyms: Asclepias longifolia var. hirtella


  • Distinguishing characteristics: Tall green milkweed can be distinguished from other milkweeds by its narrow leaves and the often drooping, umbels that are often greenish-white on short pedicels, and a column separating the corolla from the base of the hoods. Of the other milkweeds that are found in wet or mesic prairies, swamp milkweed (A. incarnata) is taller and has bright pink flowers, prairie milkweed (A. sullivantii) has wider, smooth leaves with no petioles and common milkweed (A. syriaca) has wide, hairy leaves. Short green milkweed (A. viridiflora) may look similar but is found in dry prairies, has slightly wider leaves that are not as folded along the midvein and has smaller (less than hemisperical) umbels
  • Flower characteristics: Umbels numerous and spread along upper half of stem, on short peduncles (1-2cm long); petals reflexed, green or sometimes with pink hue and separated from hood; horns (projections from hoods) none.
  • Fruit characteristics: Pods short hairy, without warty bumps.
  • Leaf characteristics: Leaves alternate or sub-opposite, narrow linear, hairy, often folding upward.


  • Blooming phenology: in June through August
  • Fruiting phenology:
  • Optimum time to identify: The optimal identification period for this species is in June through August


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated species: Phlox pilosa, Tradescantia, Allium cernuum, Eryngium yuccifolium, Liatris pycnostachya, Baptisia leucophaea.

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 Green Milkweed (Asclepias hirtella). 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 hirtella in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusSC
Federal Status in Wisconsinnone
State RankS2
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 wet to dry prairies.
  • Soils:

Natural communities

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

Ecological landscapes

This table lists the ecological landscape association scores for Green 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.

  • No avoidance measures have been developed for this species.

Management guidance

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

  • No guidance has been developed for this species.


Green Milkweed Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Green Milkweed Photo.

Photo by Kevin Doyle, Wisconsin DNR.

Green Milkweed Photo.

Photo © Derek Anderson.

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