Cirsium pitcheri (Torr.) Torr. & A. Gray
Common Name: DUNE THISTLE, PITCHER'S THISTLE

Coefficient of Conservatism: 10
Coefficient of Wetness: 5
Wetness Index: UPL
Physiognomy: Nt B-Forb
Status: T
Cirsium pitcheri forma magenteum E. G. Voss forma magenteum

Endemic to the sand beaches and dunes of Lakes Michigan and Huron, and at two sites on Lake Superior. Listed as threatened under both Michigan and Federal law.

This thistle was first noted by Zina Pitcher “on the great sand banks of Lake Superior,” presumably the Grand Sable Dunes and during the 1826–1828 period when Pitcher was stationed as an Army surgeon at Fort Brady (Sault Ste. Marie). This is a relatively mild thistle, with only short spines at the tips of the leaf lobes and the phyllaries. The whitish foliage and flowers set this apart from all our other thistles, but they blend well with the dunes on which it grows. A first-year seedling consists of a very small rosette of leaves, but rosettes in subsequent years are more robust, from a very deep taproot, and flowering usually occurs in 2–8 years, after which the plant dies. (The species is monocarpic, not strictly a biennial) The fragrant flowers are popular with insect visitors and heads can be as broad as 5 cm at full bloom. Plants are occasionally well over 1 m tall, but are usually shorter and may be quite bushy-branched or single-stemmed. Plants with numerous heads may bloom over a long period (2 months), starting in late June. At one site in Mackinac Co., plants occur with striking deep purple heads, f. magenteum E. G. Voss (2001).

Locations

Alcona County
Alger County
Allegan County
Alpena County
Antrim County
Arenac County
    Including Charity Island
Benzie County
Berrien County
Charlevoix County
    Including Beaver Island
Cheboygan County
Chippewa County
Delta County
Emmet County
Grand Traverse County
Huron County
Iosco County
Leelanau County
    Including Fox Islands
    Including Manitou Islands
Mackinac County
    Including Bois Blanc, Mackinac, Round Islands
Manistee County
Mason County
Muskegon County
Oceana County
Ottawa County
Presque Isle County
Schoolcraft County
Van Buren County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. September 21, 2014. http://michiganflora.net/species.aspx?id=290.