Synonyms: Carduus muticus.
Swamp Thistle is an uncommon plant in Maryland. It has a limited and scattered distribution. It is ONLY found growing in wet environments. If you see a thistle, and its feet are not wet, it is not a Swamp Thistle! The 2018 Maryland RTE Plant List says, "Swamp Thistle [can be found in] wet meadows, acidic seepage swamps, and mountain peatlands."
Cirsium thistles can be an identification challenge. Our first identification clue is habitat. Like we mentioned above, if the thistle's feet are not wet, it is not Swamp Thistle. The second identification point is made by Chris Frye, our Maryland State Botanist. Chris says, "Swamp Thistle is the only Cirsium thistle that you can grab and it doesn't hurt." Unlike many of Maryland's other Cirsium thistles, the spines of Swamp Thistle are not stiff enough to cause any pain. The third identification point is that the phyllaries do not have strong spiny tips.
There are 19 records in the project database.
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