| Author | Michaux | |
| Distribution | Mostly the Mountains and northern Piedmont; scattered records elsewhere in the Piedmont, and two records for the lower Coastal Plain. The Moore County record is based on a specimen at herbarium CM, collected at "Pine Bluff", but no photo is available.
Newf. to Sask., south to NC, TN, and MO. | |
| Abundance | Uncommon across the Mountains, but mostly rare to very uncommon in the Piedmont; perhaps very rare in some areas of the Piedmont. Seems to be most numerous in the southern Mountains. Extremely rare in the Coastal Plain. | |
| Habitat | Generally a wetland thistle, found in wet to damp soil of various types of swamps and swampy openings, wet meadows, marshes, and seepage slopes. | |
| Phenology | Flowering and fruiting August-November. | |
| Identification | Swamp Thistle is one of our tallest thistles, typically 4-6 feet tall but at times up to 8-9 feet tall, with numerous purple-pink heads. From all other species it differs in lacking spines on the flower head bracts (at most a tiny one less than 2 mm long). This character must be noted when distinguishing it from C. altissimum and C. discolor. When you squeeze the bracts, you will note its stickiness, a good identification character. | |
| Taxonomic Comments | None
| |
| Other Common Name(s) | Marsh Thistle | |
| State Rank | S2S3 [S3] | |
| Global Rank | G5 | |
| State Status | | |
| US Status | | |
| USACE-agcp | OBL link |
| USACE-emp | OBL link |
