Species Profile

Nugget Moss

Scientific Name: Microbryum vlassovii
Taxonomy Group: Mosses
Range: British Columbia
Last COSEWIC Assessment: November 2016
Last COSEWIC Designation: Endangered
SARA Status: Schedule 1, Endangered

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

Image of Nugget Moss


Nugget Moss is a small moss, less than 2 mm tall, that grows as erect individuals or in small, scattered patches. The leaves are light green to yellow-green or golden green, about 1 mm long, and usually somewhat concave or prow-shaped above. The leaf midrib is pale brown and often wider near the apex than below. In this species, both male and female structures are present on each plant. Sporophytes, which produce spores, mature in late winter or in spring and are immersed in the leaves. The spores, which germinate and grow into new plants, are held in a rounded capsule with a tiny point at the top. Unlike most mosses, the capsules of Nugget Moss do not have a lid that opens to release the spores. Instead, the capsule wall disintegrates as conditions dry into the summer.


Distribution and Population

Nugget Moss is extremely rare in western North America, where it has been reported from only southern British Columbia and California. It also occurs in western Eurasia, where it is rare. In Canada, it has been reported from two locations in south-central British Columbia (east of Kamloops and on the east side of Penticton). Only the Penticton population was confirmed during the most recent survey. No precise information is available on population condition or trends for Nugget Moss in British Columbia. Only one population consisting of eight individuals in two small patches was recently re-located. The extremely small population makes Nugget Moss particularly vulnerable.



In British Columbia, Nugget Moss is restricted to undisturbed, exposed, compact silts and clays on post-glacial lacustrine banks in semi-arid grassland and steppe environments where vegetation is sparse. Nugget Moss grows on the partially shaded or highly exposed steep slopes of these banks, where few other moss species are able to grow.



Nugget Moss is inconspicuous and grows as individuals or in small, scattered patches on compact, clay-rich soil. Although production of sporophytes is common in Canadian populations, only immature capsules have been observed to date. It is likely that this species needs a relatively prolonged wet spring to enable the spores to mature. Spores, if produced, are probably of importance in the short-range dispersal of this species. Nugget Moss may be a perennial species, since tuber-like structures (absorbent root-like filaments) have been observed on the rhizoids. These “tubers” rich in reserve foods may also be of importance in the survival of the species.



The habitat of this species is threatened by road construction and maintenance. Both reported sites in British Columbia are adjacent to roadways and road expansion. Recreational hiking is also a threat, since both sites are near residential areas.



Federal Protection

The Nugget Moss 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.

Nugget Moss is not protected under any provincial legislation in British Columbia.

Provincial and Territorial Protection

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


Recovery Initiatives

Status of Recovery Planning

Recovery Strategies :

Name Recovery Strategy for the Nugget Moss (Microbryum vlassovii) in Canada
Status Final posting on SAR registry



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.

8 record(s) found.

COSEWIC Status Reports

  • COSEWIC Assessment and Status Report on the Nugget Moss (Microbryum vlassovii) in Canada (2007)

    The Nugget Moss, Microbryum vlassovii, is one of four species previously included in Phascum in North America. It was known earlier as Phascum vlassovii. It is characterized by the strongly ornamented, sometimes bottle-shaped cells that are present on the upper surface of the leaf lamina and mid-rib, as well as hidden capsules that do not have a lid for spore release.

COSEWIC Assessments

Response Statements

  • Response Statement - Nugget Moss (2007)

    In North America, this globally rare moss is known from only three localized sites. Two of these sites are in semi-arid areas of south-central British Columbia. Recent surveys have re-located the species at only one of these. This moss grows on fine soils on the steep portions of silt banks in early stages of plant community development. The extremely small populations render this moss vulnerable to disturbance. Threats include potential road development and maintenance of existing roads, and collection of specimens.

Recovery Strategies

  • Recovery Strategy for the Nugget Moss (Microbryum vlassovii) in Canada (2012)

    The Nugget Moss was listed on Schedule 1 of the Species at Risk Act (SARA) as Endangered in March 2009. In the spirit of cooperation of the Accord for the Protection of Species at Risk, the Government of British Columbia has given permission to the Government of Canada to adopt the “Recovery strategy for the nugget moss (Microbryum vlassovii) in British Columbia” under Section 44 of the Species at Risk Act. As the competent minister under SARA, the federal Minister of the Environment has included an addition (Part 1) which completes the SARA requirements for this recovery strategy, and excludes the section on Socio-Economic Considerations. Socio-economic factors are not part of the consideration process for federal recovery strategies developed under SARA. These factors are kept isolated from this strategic phase of recovery planning. The British Columbia Ministry of Environment led the development of the attached recovery strategy for the species (Part 2) in cooperation with Environment Canada.


COSEWIC Annual Reports

  • COSEWIC Annual Report - 2007 (2007)

    2007 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 (2008)

    As part of its strategy for protecting wildlife species at risk, the Government of Canada proclaimed the Species at Risk Act (SARA) on June 5, 2003. Attached to the Act is Schedule 1, the list of the species that receive protection under SARA, also called the List of Wildlife Species at Risk. Please submit your comments by March 25, 2008 for species undergoing normal consultations and by March 27, 2009 for species undergoing extended consultations.