Hill’s thistle (Cirsium hillii) COSEWIC assessment and status report: chapter 1

Assessment Summary – November 2004

Common name: Hill's Thistle

Scientific name: Cirsium Hillii

Status: Threatened

Reason for designation: This is a perennial herb restricted to the northern midwestern states and adjacent Great Lakes that is found in open habitats on shallow soils over limestone bedrock. In Ontario, it is found at 64 extant sites but in relatively low numbers of mature flowering plants that are estimated to consist of fewer than 500 individuals. Some populations are protected in national and provincial parks, however, the largest population is at risk from aggregate extraction. On-going risks are present from shoreline development, ATV use, and successional processes resulting from fire suppression within its habitat.

Occurrence: Ontario

Status history: Designated Threatened in November 2004. Assessment based on a new status report.