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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: 
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. 
Flowers: 
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. 
Stem: 
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. 
Range:
 Swamp thistle is distributed across North America. 
  
References:

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 (http://plants.usda.gov).  National Plant Data Center, Baton Rouge, LA 70874 USA.

NDSU Extension Service, North Dakota State Univeristy.
http://www.ag.ndsu.nodak.edu/inaviseweeds/swamp.htm

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