Cirsium muticum (Swamp Thistle)

Plant Info
Also known as:
Family:Asteraceae (Aster)
Life cycle:biennial
Habitat:part shade, sun; swamps, bogs, wet meadows, moist open woods
Bloom season:July - October
Plant height:3 to 8 feet
Wetland Indicator Status:GP: FACW MW: OBL NCNE: OBL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: indistinct Cluster type: round

[photo of flowers] Deep purple to pink flower heads rarely more than 1½ inches wide. Bracts are typically spineless, deep green and elongated with a white stripe down the center and a cottony webbing between the bracts.

Leaves and stem: Leaf attachment: alternate Leaf type: lobed Leaf type: simple

[photo of leaves] Leaves are deeply lobed, nearly spineless, and often widely spaced on the stem. Lower leaves can be up to 8 inches long by 3 inches wide. Younger leaves can be whiteish underneath becoming smoother above and below with maturity. Stems are slender to lanky and well branched. Lower stems are sparsely woolly to almost smooth on upper growth.


Swamp Thistle is frequent in wet meadows and moist woodlands throughout east central and all of northern Minnesota. While it may grow as tall as 8 feet, 5 feet is more typical. It is fairly easy to recognize from the mesh of cob-webby hairs on the spineless bracts, and its wetland habitat.

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More photos

Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk, taken in Blaine, Anoka County, and a wooded road margin in Chisago County, MN


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Sarah - ~10 miles N of Pillager, MN
on: 2013-08-01 10:08:24

~30 plants scattered in wet meadow, private land. Photos taken of flowers in bloom.

Posted by: Sarah - Superior Hiking Trail Between Duluth and Two Harbors
on: 2013-09-22 22:08:08

A few plants in wet grassland area. In bloom late August 2013

Posted by: Paula
on: 2016-07-17 11:22:35

New to Duluth, MN. Should all thistles be gotten rid of or are there some that are good?

Posted by: K. Chayka
on: 2016-07-17 11:37:13

Paula, there are 10 thistle species in Minnesota, half of which are native. The natives are extremely beneficial to native insects and birds and should be encouraged. A good rule of thumb for determining the good from the bad: the weeds are typically very sharply prickly where the natives are softly prickly at their worst. Also, the leaves of many of the natives are white on the underside where the weeds are more green. Note, however, that the Duluth area is "weed central" in MN so you may have more of the exotics than natives in your area.

Posted by: Brett - Otsego
on: 2019-11-13 18:46:18

First time noticing this in September at Lyndon Cedarblade Park (Isanti County) and while going through old pictures from 2014 at Savanna Portage SP.

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