Wednesday, October 2, 2013

Native Species Profile - Pitcher's Thistle

Coastal Dune - Lake Huron

Coastal dunes are among the most threatened habitats in the Great Lakes. They can exist only in certain places along the shorelines of the lakes and many are under constant threat of development. Despite their close proximity to water, the dunes themselves are arid habitats.  For plants to survive in this habitat they have to be tough.  Some of the plants found here are endemic to this habitat - this mean they are found nowhere else on earth.  One of the endemic plants of the western Great Lakes is the Pitcher's Thistle (Cirsium pitcheri).

Coastal Dune community with Pitcher's Thistle front and center

Pitcher's Thistle, also known as Sand Dune Thistle, can only be found on the shorelines of Lakes Huron, Michigan, and Superior.  The species is listed as Threatened by the US government and Endangered by the government of Canada.  While Pitcher's Thistle can be found in Wisconsin, Indiana, and Ontario (The species is extinct in Illinois), the bulk of Pitcher's Thistle populations can be found in Michigan.  Populations exist all along Michigan's Lake Michigan shoreline north to the Straits of Mackinaw, south along the Lake Huron shoreline to Saginaw Bay, and in the Upper Peninsula along the north shore of Lake Michigan.  A small population is also found in the Grand Sable Dunes along Lake Superior.

Pitcher's Thistle growing on the Lake Huron Shoreline at P. H. Hoeft State Park near Rogers City, MI

Pitcher's Thistle is a has silver-gray foliage and may grow to reach heights of over 3 feet, but is often much shorter.  The leaves are deeply lobed and almost skeletal in appearance.  For a thistle, the plant has very few spines. 

Pitcher's Thistle - note the white flowers and silver-grey foliage

Pitcher's Thistle is a short-lived perennial,  growing steadily for two to eight years until it stores enough energy in its deep taproot to flower.  After producing one or more white blooms the plant dies.  The plant flowers between May and September.  Like other thistle species, the seeds of Pitcher's Thistle are distributed by the wind. 

Pitcher's Thistle is an early successional species.  It is able to become established on bare sand, but is crowded out by other plants.   It does best on shorelines and dunes that are frequently disturbed by natural processes of wind and water erosion.

Pitcher's Thistle blooms

Basic Information

Pitcher’s Thistle 
Cirsium pitcheri

Height:  up to 3’ tall

Habitat:  dunes, shorelines of Lakes Michigan, Superior, and Huron

Flower Color:  white

Bloom Time:  May – September

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