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University of Guelph


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Hill’s Thistle

GRIPP Hills Thistle Cirsium hillii

Species name

Cirsium pumilum var. hillii (Canby) B. Boivin (Synonym: Cirsium hillii (Canby) Fern)

Conservation Status in Canada

According to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), this species was listed as endangered in 2004. It is also listed as schedule 1 and endangered under the Species At Risk Act (SARA).

Distribution and Habitat

Hill’s thistle is distributed around the Great Lakes region of North America, spanning from southern Ontario, to Michigan, Wisonsin, Minnesota, Iowa, Illinois, and In diana. In Canada, there are 64 known populations located on Manitoulin Island and the west side of the Bruce Peninsula. This species is endemic to North America, and in Canada is found on open, shrubbed,or treed alvar communities as well as in landscapes which have historically been disturbed by drought or fire.

Why this Species Matters

This species is characteristic of alvar communities which are currently very restricted in Canada, with 60% being found in Ontario. Globally, alvars are considered rare, hosting open habitats with a limestone or dolostone base which may or may not be covered with a thin layer of soil. Despite appearing almost barren, these communities are species rich, providing habitat for a diverse species which exist nowhere else in the world (Nature Conservancy of Canada 2018).

  • Lack of suitable habitats due to fire suppression
  • Building and Road Construction
  • Recreational activities, ATVs, and pedestrians
What is GRIPP doing?

Using in vitro technologies, GRIPP researchers developed plant tissue culture protocols for mass producing Hill’s Thistle, and in the summer of 2017, 300 plants were planted in the Bruce Peninsula. GRIPP is currently working with Parks Canada staff to monitor the long-term survival of plants in the wild, in hopes of re-introducing more individuals in the future. Additionally, GRIPP is currently working to develop protocols for long-term storage of germplasm (also known as cryopreservation) so that the long-term survival of this species is secure.

Read a full report on the conservation status of this species.
Read a full report on the recovery strategy for this species.