Dunce-nettle Cirsium muticum
Other Common Name(s):
- Phonetic Spelling
- SIR-see-um mu-tee-kum
- Description
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Swamp Thistle is a native biennial plant in the Asteraceae (daisy) family that is native to central and eastern Canada and the United States. Its name comes from the Greek kersion which means thistle. The specific epithet comes from the Latin word muticus, meaning blunt referring to its phyllaries. The plant has tall branching stems that contain purple to pink flowers on spineless bracts. The plant often grows 2 to 5 feet tall (sometimes as high as 8 feet depending on the moisture level) with clasping leaves that are 10 inches long and 4 inches across. It is found in wet soil in meadows, prairies, marshes, swamps, bogs, and open woods.
Swamp thistle prefers full sun, wet to moist conditions and grows best in sandy soil although partial sun and other soil types are tolerated. It is propagated via seed, but expect it to take two years until it flowers. It forms a rosette of leaves the first year and sends up a flowering stem the second year with a solitary flower or a cluster of flowers. This thistle has fewer spines than some and is much easier to control than other thistles.
The thistle is a high-value nectar plant for bees and butterflies and the songbirds eat the seeds and use the tufts of the seeds for their nests. The seeds are rich in oil, an important food source for seed-eating birds. It is the host plant for the Swamp metalmark (Calephelis muticum) moth and the Painted lady (Vanessa cardui) butterfly as well as beetles, grasshoppers, and weevils. Flowers are also attractive to hummingbirds. Members of this genus support the following specialized bees: Thistle Long-horned bee Melissodes desponsus, plus Osmia (Helicosmia) chalybea and Osmia (Helicosmia) texana.
Swamp thistle is a great option in the wetlands of your meadow garden or naturalized area when looking for native host plants for the Swamp Metalmark butterfly or the Painted Lady butterfly. They are used to make decorative arrangements. If you want to plant a thistle in your gardens, this is the one to plant because they are easier to control than other thistles. They are non-invasive in North Carolina.
Quick ID Hints:
- In a wetland habitat, the bracts are spineless and contain a mesh of cob-webby hairs.
- White densely wooly underside of the leaves.
Insects, Diseases, and Other Plant Problems: No significant problems.
- See this plant in the following landscape:
- Cultivars / Varieties:
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- Tags:
- Cultivars / Varieties:
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- Tags:
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Attributes:
- Genus:
- Cirsium
- Species:
- muticum
- Family:
- Asteraceae
- Life Cycle:
- Biennial
- Recommended Propagation Strategy:
- Seed
- Country Or Region Of Origin:
- Central and eastern Canada and United States
- Distribution:
- Prairies of southeastern Saskatchewan across southern Canada to Newfoundland and south in the United States from North Dakota and Maine to southeastern Texas and northern Florida.
- Wildlife Value:
- Members of the genus Cirsium support the following specialized bees: Melissodes (Heliomelissodes) desponsus, Osmia (Helicosmia) chalybea and Osmia (Helicosmia) texana. Birds eat the seeds.
- Particularly Resistant To (Insects/Diseases/Other Problems):
- Tolerant of wet soils and are not often visited by deer.
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Whole Plant Traits:
- Plant Type:
- Native Plant
- Weed
- Wildflower
- Habit/Form:
- Erect
- Growth Rate:
- Medium
- Maintenance:
- Low
- Texture:
- Coarse
- Appendage:
- Prickles
- Spines
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Cultural Conditions:
- Light:
- Full sun (6 or more hours of direct sunlight a day)
- Soil Texture:
- Sand
- Soil pH:
- Acid (<6.0)
- Alkaline (>8.0)
- Neutral (6.0-8.0)
- Soil Drainage:
- Moist
- Occasionally Wet
- Available Space To Plant:
- 12 inches-3 feet
- NC Region:
- Coastal
- Mountains
- Piedmont
- USDA Plant Hardiness Zone:
- 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
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Fruit:
- Fruit Color:
- Cream/Tan
- Fruit Value To Gardener:
- Showy
- Display/Harvest Time:
- Fall
- Fruit Type:
- Achene
- Fruit Length:
- < 1 inch
- Fruit Width:
- < 1 inch
- Fruit Description:
- Seeds are produced singly in a flat, dark brown fruit about 1/10 of an inch long. Seeds produce a feathery pappus (similar to dandelion ‘seeds’) which help disperse the seeds.
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Flowers:
- Flower Color:
- Pink
- Purple/Lavender
- Flower Inflorescence:
- Head
- Flower Value To Gardener:
- Good Cut
- Showy
- Flower Bloom Time:
- Fall
- Summer
- Flower Shape:
- Dome
- Flower Size:
- 1-3 inches
- Flower Description:
- Purple to pink flower heads are a dense cluster of numerous disk florets up to 2.5 inches wide on a hollow flowering stem. The sticky bracts are not tipped with spines. Blooms late summer to fall.
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Leaves:
- Leaf Color:
- Green
- Leaf Feel:
- Prickly
- Leaf Type:
- Simple
- Leaf Arrangement:
- Alternate
- Rosulate
- Leaf Shape:
- Elliptical
- Obovate
- Ovate
- Pinnatifid
- Leaf Margin:
- Lobed
- Hairs Present:
- Yes
- Leaf Length:
- > 6 inches
- Leaf Width:
- 3-6 inches
- Leaf Description:
- Rosette of long-stalked, deeply incised leaves up to 16 inches long and 4 inches across growing alternately on the stem. They are pinnately cut into broad prickly segments with spiny tips. The leaves become gradually smaller in size as they grow up the stems. The top of the leaves are green but the underside is whitened from a dense coating of white hairs when the leaves are young. These hairs thin when older and the underside of the leaf becomes pale green.
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Stem:
- Stem Color:
- Green
- Stem Is Aromatic:
- No
- Stem Cross Section:
- Round
- Stem Surface:
- Hairy (pubescent)
- Stem Description:
- Green finely grooved longitudinally.
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Landscape:
- Landscape Location:
- Meadow
- Naturalized Area
- Landscape Theme:
- Native Garden
- Pollinator Garden
- Attracts:
- Butterflies
- Moths
- Pollinators
- Songbirds
- Specialized Bees
- Problems:
- Spines/Thorns
- Weedy
