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Circium muticum

Common Name of Species: Swamp Thistle  
Family: Asteraceae

Entry Author:  C. Friedl, Muhlenberg College
Key Characteristics: Swamp thistle can be identified by its hollow stems and its bracts which are sticky and cobwebby. 

Leaves are divided, with very deep lobes and sharp prickles.  Can be as long as 10 inches, and as wide as 4 inches. Leaf width gets smaller towards the stem of the leaf.  Essentially lanceolate in in shape. 
Flower bracts are prominent and sticky like cobwebs.  The bracts are not sharp or spiny like the bracts of other thistles.  The flower head are approximately 1.5-2 inches wide, and are deep purple or lavender in color.  Petals are tubular, small and erect, creating a bell shape. Flower can grow in small clusters or alone. 
Stems are hollow, ribbed and smooth, with possible branching towards the very top. 
Height: Can grow to be 3-6 feet in height.  
Branching Pattern of Leaves:  Leaves grow alternate to one another. 
Conditions/Habitat: Tends to grow in wet, swampy places, including low meadows and wet thickets. 
 Swamp thistle is distributed across North America. 

Newcomb, Lawrence (1977).  Newcomb’s Wildflower Guide.  New York: Little, Brown.

McKenny, M. & Peterson R.T. (1996). Peterson Field Guides: Wildflowers Northeastern/ North-central North America. New York: Houghton Mifflin.

USDA, NRCS (2004). Plants Database, Version 3.05 (  National Plant Data Center, Baton Rouge, LA 70874 USA.

NDSU Extension Service, North Dakota State Univeristy.

This page was created by: C. Friedl, Muhlenberg College
Last updated 12/16/05