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Hill's Thistle (Cirsium hillii)

Life history

Species overview

Hill's Thistle (Cirsium hillii), a Wisconsin Threatened and Federal Species of Concern plant, is found in dry prairies and oak barrens; in neighboring states it is found in pine barrens. Blooming occurs mid June through early August; fruiting occurs late July through late August. The optimal identification period for this species is mid June through late August.

Synonyms: Cirsium pumilum ssp. hillii, Cirsium pumilum var. hillii, Cnicus hillii


  • Distinguishing characteristics: Distinguished from canada thistle (C. arvense) by its basal rosette and long phyllaries, and from bull thistle (C. vulgare) by its shorter stature and lack of spiny wings on the stem.
  • Flower characteristics: A few (1 to 3), large, solitary flower heads (3.5 to 6 mm broad) have sweet-scented purple flowers; flower heads subtended by 2 to 5 mm long phyllaries (involucral bracts) tipped with a spine.
  • Fruit characteristics: Seeds usually 4 to 5 mm in length.
  • Leaf characteristics: Deeply lobed with large and small spines along the edges; basal rosette and lower cauline leaves 12 to 25 cm long x 2 to 7 cm wide.


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


  • Growth form: Forb-erect
  • Vegetative reproduction:
  • Life cycle: Perennial
  • Comments: Associated Species: Quercus ellipsoidalis, Pinus banksiana, Andropogon gerardii, A. scoparius, Panicum virgatum, Aster spp., Solidago spp.

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 Thistle (Cirsium 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 Cirsium hillii in the Natural Heritage Inventory Database as of July 2015.

Summary Information
State StatusTHR
Federal Status in WisconsinSOC
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 in dry prairies and oak barrens; in neighboring states it is found in pine barrens.
  • Soils: Dry, sandy soils.

Natural communities

This table lists the natural communities that are associated with Hill's Thistle. 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
Dry Prairie 3
Dry-mesic Prairie 2
Sand Prairie 2

Ecological landscapes

This table lists the ecological landscape association scores for Hill's Thistle. 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

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


Hill's Thistle Photo.

Photo © Jan Axelson.

Hill's Thistle Photo.

Photo © Cathy Bleser.

Hill's Thistle Photo.

Photo by Thomas Meyer, Wisconsin DNR.

Hill's Thistle Photo.

Photo by Armund Bartz, Wisconsin DNR.

Hill's Thistle Photo.

Photo © Kitty Kohout.

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