Species Profile

Hill's Thistle

Scientific Name: Cirsium hillii
Taxonomy Group: Vascular Plants
COSEWIC Range: Ontario
COSEWIC Assessment Date and Status Change: November 2004
COSEWIC Status: Threatened
COSEWIC Status Criteria: Met criterion for Endangered, C2a(i), but designated Threatened, C2a(i); D1, because the species is not at imminent risk of extirpation due to the occurrence of numerous sites, some in protected areas.
COSEWIC 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.
COSEWIC History of Status Designation: Designated Threatened in November 2004.
SARA Status: Schedule 1, Threatened
Date of Listing (yyyy-mm-dd): 2006-08-15

Please note that this information is provided for general information purposes only. For the most up to date and accurate list of species listed under the Species at Risk Act, please see the Justice Laws Website.

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Quick Links: | Description | Distribution and Population | Habitat | Biology | Threats | Protection | Recovery Initiatives | National Recovery Program | Documents

Hill's Thistle Photo 3

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Description

Hill's Thistle is a perennial herb measuring 25 to 60 cm in height. Stems are soft and ridged with a more or less thin covering of hairs. They bear a few leaves, which become progressively smaller nearer the tip. Although the leaves are often smooth, the undersides may be sparsely covered in woolly hairs. The leaf margins are typically undulated. One or two short branches develop near the top of the stems. Each branch bears one or several large heads measuring 3.5 to 5 cm in diameter with several tightly grouped small flowers. The flowers are deep pink to purple and, occasionally, white. At the base of the plant, there is a rosette of long elliptic leaves with rounded edges.

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Distribution and Population

Hill's Thistle is native to North America and occurs primarily in the Great Lakes area. It can be found from southern Ontario to Michigan, Wisconsin, Minnesota, Iowa, Illinois and Indiana. In Canada, Hill's Thistle is limited to southern Ontario, where there are 70 documented sites. Most of these sites are on the shores of Manitoulin Island, located in the northern part of Lake Huron, and on the west shore of the Bruce Peninsula. It is likely that six of these sites have disappeared. Mature flowering plants occur in relatively low numbers in the 64 confirmed Ontario sites. The Canadian population of mature plants capable of reproducing is estimated at fewer than 500 individuals. Since virtually all the surveys were conducted between 1995 and 2003, it is impossible to identify long-term trends for this population. While the largest populations are all likely known, there may be other significant, as yet undiscovered populations in other locations.

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Habitat

Hill's Thistle grows in a variety of open, dry, sandy and fire-prone environments. Such environments include grasslands covering gravel hills or escarpments, dry sandy grasslands, oak-pine barrens, dunes, oak savannahs and open woods. In Ontario, this species grows primarily in alvar grasslands; these habitats are characterized by limestone outcrops, shallow soil and sparse vegetation. Hill's Thistle often shares these environments with other herbaceous species, particularly Poverty Oat-grass and Bearberry, under a forest cover of Jack Pine, White Spruce, and Eastern White Cedar. The shoreline alvars of Manitoulin Island, neighbouring islands and the western shores of the Bruce Peninsula are vital to the long-term survival of Canadian Hill's Thistle populations.

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Biology

Little is known about the biology of Hill's Thistle. However, it is known to be a perennial plant with a short lifespan; it typically lives two or three years, rarely living more than four or five. Although flowering can occur one or two years after the establishment of the basal leaf rosette, Hill's Thistle typically flowers in its third year. This species can reproduce vegetatively through new rosettes that emerge from buds that form on some roots. In Ontario, this perennial blooms from mid-July to late August and its flowers are pollinated by bees. The plant typically produces a large quantity of seeds that are disseminated by the wind. It is believed that an overly dense layer of vegetation on the ground could hinder germination. The main factor that limits this species’ ability to reproduce appears to be the increase of the surrounding forest cover and the resulting decrease in available light. Flowers and seeds are vulnerable to insects and perhaps fungi.

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Threats

While there are a number of factors that limit the Canadian population of Hill's Thistle, the most significant factor is the severely limited size of the alvars where this species grows. These open environments are among the most threatened in North America and Ontario. What is left of these environments is being lost to the succession of vegetation that occurs naturally. In the absence of natural events such as fire that serve to keep these environments open, these areas are becoming less and less suitable habitats for Hill's Thistle. The biggest threat to the majority of Ontario’s populations of Hill's Thistle is the progressive loss of this species’ habitat to the construction of permanent residences on private properties that are located in one of the province’s most scenic shoreline areas. In addition, the site that contains the largest number of mature individuals is licensed for the extraction and crushing of limestone aggregates. All-terrain vehicles have damaged several of the alvars in which this species occurs, due to the popularity of these open areas for ATV use. Finally, certain invasive species could have a possible impact on Hill's Thistle in Ontario.

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Protection

Federal Protection

The Hill's Thistle is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

In Ontario, Hill’s Thistle is not protected under any provincial law. Of the 64 sites where this species currently occurs, 11 are in national parks, where the species is protected under the Canada National Parks Act, or in provincial parks, where it is afforded a certain degree of protection.

Provincial and Territorial Protection

To know if this species is protected by provincial or territorial laws, consult the provinces' and territories' websites.

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Recovery Initiatives

Status of Recovery Planning

Recovery Strategies :

Name Recovery Strategy for the Hill's Thistle (Cirsium hilli) in Canada
Status Final posting on SAR registry

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Recovery Progress and Activities

Summary of Progress to Date In 2005, 633 plants (23 in flower) were found at 28 sites at Wasaga Beach. Only 16 flowering plants were found in 2004. Summary of Research/Monitoring Activities In 2005, staff at Wasaga Beach Provincial Park monitored and reported on their population of Hill’s Thistle. There is now good information on the current status of Hill’s Thistle at the park. URLs COSEWIC Assessment and Status Report: Hill`s Thistle:http://dsp-psd.pwgsc.gc.ca/Collection/CW69-14-425-2005E.pdf

Documents

PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.

10 record(s) found.

COSEWIC Status Reports

  • COSEWIC assessment and status report on Hill's thistle Cirsium hillii in Canada (2005-08-12)

    Hill's thistle is a short (25 to 60 cm tall) perennial thistle with a deep, hollowed, clustered root system. The leafy stems are soft, ridged, and either sparsely hairy or with woolly hairs; with 1 or 2 short branches near the top terminating in one to several large heads (3.5 to 5 cm) with deep pink-purple, or occasionally white, flowers.

Response Statements

  • Response Statements - Hill's Thistle (2005-11-15)

    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.

Recovery Strategies

  • Recovery Strategy for the Hill's Thistle (Cirsium hillii) in Canada (2011-07-06)

    Hill's Thistle (Cirsium hillii) is listed as Threatened under Schedule 1 of the federal Species at Risk Act (SARA). In Ontario, it is listed as Threatened on the Species at Risk in Ontario (SARO) List under the Endangered Species Act, 2007 (ESA). The global rank of Hill's Thistle is vulnerable, and is completely restricted to the Great Lakes Region. The Canadian range of Hill's Thistle may account for as much as 50% or more of the global population. The first version of this recovery strategy was originally posted in 2011. The current version posted here has been amended, as per Section 45 of the Act, from the first version, to include some additional language regarding Traditional Ecological Knowledge.

Action Plans

  • Multi-species Action Plan for Bruce Peninsula National Park and Fathom Five National Marine Park of Canada (2016-11-22)

    Bruce Peninsula National Park (BPNP) and Fathom Five National Marine Park (FFNMP) lie at the tip of the Bruce Peninsula which separates Georgian Bay from Lake Huron. The peninsula is 90 km in length and its most prominent feature is the Niagara Escarpment which runs along the entire eastern edge. Within BPNP, the escarpment forms the Georgian Bay shoreline and is recognized as part of the core area of the Niagara Escarpment UNESCO World Biosphere Reserve.  BPNP was established by the federal government in 1987 to protect a representative example of the Great Lakes/St. Lawrence Lowlands natural region. Because of the fragmented nature of the park properties, many of the stresses on the park’s ecosystem originate from outside its boundaries. For this reason, First Nations, local residents, non-governmental organizations, and other groups and land users play an important role in managing, restoring, and protecting the northern Bruce ecosystem. 

Orders

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2005 (2005-08-12)

    2005 Annual Report to the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.

Permits and Related Agreements

  • Explanation for issuing permit(#3128), persuant to the provisions of section 73 of SARA (2009-06-15)

    Dr. Joanna Freeland, Trent University, will conduct an assessment of the genetic diversity within and between Hill's thistle (Cirsium hillii) populations at Bruce Peninsula National Park and region. The objective is to: 1. Identify high risk populations, e.g. isolated populations with low genetic diversity and/or high inbreeding. 2. Identify key populations, e.g. source populations, or genetically divergent populations, which make a disproportionately large contribution to overall genetic diversity. 3. Compare locations of key Hill's thistle populations to those of key Pitcher's thistle populations to determine which areas could, if protected, benefit both species.
  • Explanation for issuing permit(#BPF-2015-19858), persuant to the provisions of section 74 of SARA (2015-07-20)

    A small portion of seeds will be collected from no more than ten Hill's Thistle seed heads within the Bruce Peninsula National Park. The seeds will then be used for Hill's Thistle in vitro germination in order to multiply the plants from existing populations. The main objectives of this project are to develop a protocol for in vitro propagation and long term conservation (cryopreservation) of Hill's Thistle. This will allow for potential reintroduction of Hill's Thistle in their natural environment.

Consultation Documents

  • Consultation on Amending the List of Species Under the Species At Risk Act: November 2005 (2005-11-16)

    The Government of Canada proclaimed the Species at Risk Act (SARA) on June 5, 2003 as part of its strategy for the protection of wildlife species at risk. Attached to the Act is Schedule 1, the list of the species that receive protection under SARA, hereinafter referred to as the 'SARA list'. Canadians are invited to comment on whether all or some of the species included in this document should be added to the SARA list.
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