Large-headed Woolly Yarrow
Scientific Name: Achillea millefolium var. megacephala
Other/Previous Names: Achillea millefolium var. megacephalum
Taxonomy Group: Vascular Plants
Last COSEWIC Assessment: May 2000
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern
Image of Large-headed Woolly Yarrow
As its name suggests, the Large-headed Woolly Yarrow is a densely woolly or hairy perennial plant that bears large clusters (4-10 cm in diameter) of composite flowers (6mm or more in diameter) atop erect stems that are 30-50 cm high. Like all yarrows, it has finely dissected leaves that form basal clusters and are alternately arranged along the flowerhead stems, but in this species the leaves are densely woolly. The flower clusters are composed of numerous flower heads, each of which consists of many tiny flowers surrounded by a circle of white rays. The heads are arranged in compact clusters, which are quite showy. The Large-headed Woolly Yarrow is similar in appearance to the more common Woolly Yarrow, but it is more densely woolly overall, and has larger flower heads with larger and more prominent rays.
Distribution and Population
The Large-headed Woolly Yarrow is endemic to (found only in) the Athabasca Sand Dunes of northwestern Saskatchewan, and is restricted to the western part of the dune complex. It occurs as sparsely scattered plants on two dune fields. Although no studies have been done on population size and trends, the population is believed to be stable.
The Large-headed Woolly Yarrow is a habitat specialist. It occurs on the leeward side of large, open sand dunes, in depression seams and dune slacks, and on the back slopes of large, sandy, beach ridges along the lake shore where these ridges abut on the dune fields.
The Large-headed Woolly Yarrow is a herbaceous perennial that depends on insects for pollination. It reproduces by seeds, which are likely wind dispersed, as well as vegetatively by horizontal rhizomes to form small clonal colonies.
Although the dunes occur in a remote area, threats to the yarrow from potential increased public accessibility to the dune fields include trampling and habitat disturbance by sight-seekers, eco-tourists, and various forms of recreational use of the dunes (e.g., dune buggies, motorcycles).
Federal ProtectionMore information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
The entire range of the Large-headed Woolly Yarrow is contained within Athabasca Sand Dunes Provincial Wilderness Park.
Provincial and Territorial Protection
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.
1 record(s) found.
- Management Plans (1 record(s) found.)
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