Dunce-nettle
Cirsium muticum
Last reviewed: August 2026
Cirsium muticum (Swamp Thistle) is a native wetland perennial found across eastern North America. This tall thistle blooms from July through September with purple flowers that attract bees and butterflies.
Toxicity unknown
Dunce-nettle (Cirsium muticum) is not listed by the ASPCA Animal Poison Control Center (opens in new tab) or the other sources we check, so we have no verdict for it either way. Absence from those lists is not a clearance. If your pet shows symptoms after eating any plant, call the ASPCA at (888) 426-4435.
Light
part sun
Water
medium
Size
24"–60" H × 12"–24" W
Bloom
Jul, Aug, Sep
Native to
AL, AR, CT, DE and 29 more states
Pollinators
bees, butterflies
Before you buy
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Swamp thistle is a tall native perennial that produces clusters of pink to purple flowers from summer through early fall. Despite its common name, it's not aggressive like non-native thistles and provides excellent wildlife value in naturalized settings.
Growing Dunce-nettle
Grow Dunce-nettle in part sun and medium water. Mature plants reach 24 to 60 inches tall and spread 12 to 24 inches wide. Expect low maintenance to keep it looking intentional in a front yard.
In an HOA neighborhood
Dunce-nettle takes more care to keep looking intentional in a front yard. Maintenance level: low. Consider it for backyard or mid-zone beds rather than the street edge.
Works well in: backyard only.
- Thistle appearance triggers negative associations
- Can reach 5 feet tall
- Dies back completely in winter leaving bare stems
Wildlife value
The flowers are magnets for native bees, butterflies, and other pollinators during late summer blooms. Seeds provide food for goldfinches and other birds in fall.
Common questions
- Where does Cirsium muticum naturally grow?
- Swamp Thistle is native to much of eastern North America, from Maine south to Florida and west to North Dakota, including the Great Lakes region and southeastern states.
- When does Swamp Thistle bloom?
- Cirsium muticum produces its purple flower heads from July through September, providing late-season nectar for pollinators.
- What pollinators visit Swamp Thistle?
- The flowers attract various bees and butterflies, making it valuable for pollinator gardens and natural areas.
- What growing conditions does Cirsium muticum prefer?
- This species thrives in medium to high moisture conditions and can tolerate full sun to partial shade, making it well-suited for wetland margins and moist meadows.
- Is Dunce-nettle HOA-friendly?
- Dunce-nettle takes more care to look intentional in a front yard. Consider it for backyard or mid-zone beds rather than the street edge.
These answers were drafted with an AI model from this plant's data. Verify care details with a local expert.
Native range data from the World Checklist of Vascular Plants (Kew). Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.
Ready to grow Dunce-nettle? Add it to your garden in Pollinator Patch to track it and get season-by-season care guidance.
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