Species Profile

Dwarf Woolly-heads Prairie population

Scientific Name: Psilocarphus brevissimus
Taxonomy Group: Vascular Plants
Range: Alberta, Saskatchewan
Last COSEWIC Assessment: April 2006
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern

Go to advanced search

Quick Links: | Taxonomy | Description | Habitat | Biology | Threats | Protection | Recovery Team | National Recovery Program | Documents

Image of Dwarf Woolly-heads


Two varieties of Dwarf Woolly-heads are recognized: the typical brevissimus variety and the multiflorus variety. Because this species is represented in Canada only by the brevissimus variety, the name “Dwarf Woolly-heads” is used here without specifying the variety.



The Dwarf Woolly-heads is a woolly annual with a short root. Its stems are prostrate, matted and 8 to 20 cm long. It has few leaves, which are covered with fine white woolly hairs and inserted directly into the stem in opposing pairs. They resemble triangular lances or narrow lances with their ends more or less rounded. They are 4 to 15 mm long. The flowers are grouped in disc-shaped heads located in the leaf axils where the leaves meet the branches, or at the tips of the branches. Small hooded and balloon-like leaves, 2.4 to 4 mm long, grow at the base of the flower heads. The dry fruits, called achenes, are more or less cylindrical. They are 1 to 2 mm long and hairless.


Distribution and Population

The range of Dwarf Woolly-heads extends from south-central British Columbia south to Montana and Utah in the western United States to Baja California, Mexico. It also occurs in Chile and Argentina. In Canada, Dwarf Woolly-heads is known from only the Similkameen Valley south of Princeton in south-central British Columbia and from southeastern Alberta and southwestern Saskatchewan. The Southern Mountain population (British Columbia) and the Prairie population (Alberta and Saskatchewan) are separated by a distance of over 500 km and several mountain ranges.   Like all annual plant populations of vernal pools and temporary ponds, the Prairie population fluctuates greatly from year to year, depending on rainfall and flooding. It may have as few as 2000 mature individuals in “trough” years and perhaps as many as 27 000 in “peak” years. It is therefore difficult to predict long-term trends in this population.



The Dwarf Woolly-heads grows in chalky clay soils in vernal pools in large forest openings dominated by two other flowering plants: Scouler’s Popcornflower and the Close-flowered Knotweed. This annual also grows at the edges of ephemeral ponds on this same type of soil, which is wet in spring but becomes dry and compacted in summer. The sites where the Dwarf Woolly-heads populations occur are on level to gently sloping terrain. The species shows a high tolerance both for spring floods and summer heat and drought.



Little information is available on the biology of the Dwarf Woolly-heads. However, it is known that, in British Columbia, this species flowers in June when the inundated vernal pools are increasingly saturated with water. A study of the plant’s flowers and its lack of any features to attract pollinating insects suggest that this species probably reproduces by self-pollination. This means that its flowers are fertilized by their own pollen. However, pollen may not be essential for the production of seeds and the species may in fact reproduce without fertilization. The Dwarf Woolly-heads produces its fruits when the pond has dried up. Its seeds may be dispersed by animals. Various species of birds that use the vernal ponds might carry the seeds over short or long distances. Cottontail rabbits, including Nuttall's Cottontail, which lives in the grasslands of this region, may also help to disperse seeds between vernal ponds in proximity to each other.



The factor that constitutes the most immediate threat to the populations of Dwarf Woolly-heads in British Columbia, and hence in Canada, is the smallness of the area that they occupy. This factor makes them highly vulnerable. Also, because the habitats suitable for this species are extremely limited, the opportunities for colonization and expansion are limited too. The recreational use of all-terrain vehicles, which has been observed near the Dwarf Woolly-heads sites, constitutes another definite threat. These vehicles could alter the habitat so much that it would no longer be suitable for this species and would favour invasive exotic plants. The populations are located on two private properties that are part of British Columbia’s Agricultural Land Reserve, which is mainly used for agriculture. Some of the activities allowed in the reserve are not necessarily compatible with the habitat requirements of this species. Lastly, weed-control measures pose another potential threat. The chemicals used to destroy nuisance plants are not very specific and could kill the Dwarf Woolly-heads.



Federal Protection

More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

Provincial and Territorial Protection

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


Recovery Team

Prairie Plant Species at Risk Recovery Team

  • Candace Neufeld - Chair/Contact - Environment Canada
    Phone: 306-975-4101  Send Email



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.

9 record(s) found.

COSEWIC Status Reports

  • COSEWIC assessment and status report on the dwarf woolly-heads Psilocarphus brevissimus in Canada (2006)

    Psilocarphus brevissimus is a prostrate, matted annual herb with a short taproot. The plants are from 8 to 20 cm long. The few leaves are restricted to the stems and are opposite, lance-linear to lance-oblong or lance-triangular, 4-15 mm long and white woolly-hairy. The flower heads are disciform, usually solitary in the leaf axils or at the tips of the branches and lack involucres. The receptacular bracts are 2.4-4 mm long, hooded and balloon-like. The achenes are more or less cylindric, glabrous, nerve-less and tipped with a small, 1-2 mm long, offset style. There is no pappus.

COSEWIC Assessments

  • COSEWIC Assessment - Dwarf woolly-heads (2006)

    Designated Endangered in November 2003. Renamed dwarf woolly-heads (Southern Mountain population) in April 2006 and designated Endangered. Last assessment based on an update status report.

Response Statements

  • Response Statements - Dwarf Woolly-heads (2006)

    This population is widely distributed in Saskatchewan and Alberta at more than 40 sites with large among-year fluctuations in numbers of mature individuals and with concerns over potentially significant future impacts.  These pertain to potential future development of coal-bed methane gas extraction in a significant part of the range of the population and disruptions from pipeline construction.

Management Plans


  • Order Acknowledging Receipt of the Assessments Done Pursuant to Subsection 23(1) of the Act (2007) (2007)

    This Order acknowledges receipt by the Governor in Council of the assessments of the status of 40 species done pursuant to paragraph 15(1)(a) and in accordance with subsection 23(1) of the Species at Risk Act (SARA) by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The purpose of SARA is to prevent wildlife species from being extirpated or becoming extinct, to provide for the recovery of wildlife species that are extirpated, endangered or threatened as a result of human activity and to manage species of special concern to prevent them from becoming endangered or threatened.
  • Order Amending Schedule 1 to the Species at Risk Act (2007)

    Her Excellency the Governor General in Council, on the recommendation of the Minister of the Environment, pursuant to section 27 of the Species at Risk Act, hereby makes the annexed Order Amending Schedules 1 to 3 to the Species at Risk Act.

COSEWIC Annual Reports

  • COSEWIC Annual Report - 2006 (2006)

    2006 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.

Consultation Documents

  • Consultation on Amending the List of Species under the Species at Risk Act Terrestrial Species: December 2006 (2006)

    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. Please submit your comments by March 16, 2007 for species undergoing normal consultations and by March 14, 2008 for species undergoing extended consultations.

Recovery Document Posting Plans

  • Environment and Climate Change Canada's Three-Year Recovery Document Posting Plan (2016)

    Environment and Climate Change Canada’s Three-Year Recovery Document Posting Plan identifies the species for which recovery documents will be posted each fiscal year starting in 2014-2015. Posting this three year plan on the Species at Risk Public Registry is intended to provide transparency to partners, stakeholders, and the public about Environment and Climate Change Canada’s plan to develop and post these proposed recovery strategies and management plans. However, both the number of documents and the particular species that are posted in a given year may change slightly due to a variety of circumstances. Last update March 31, 2017