Cirsium muticum Michx.

Cirsium muticum was first described by Andre Michaux in Flora boreali-american :sistens caracteres plantarum quas in America septentrionali collegit et detexit Andreas Michaux in 1803. Synonyms for this species are Carduus muticus and Cirsium muticum var. monticola.

It is a biennial forb in the lineage of true thistles. It may be distinguished from other Cirsium species by the appearance of cobweb-like hairs covering its involucres, which support pink to purple flowers. Its spines are softer and significantly less dense than other species of Cirsium by comparison, and the stem is usually entirely unwinged. It prefers wet environments, as indicated by the vernacular “swamp thistle,” and will not grow in dry soil. It tends to flower later in the summer than its relatives, from July to September. It is distributed across the entirety of eastern North America. It stretches from Manitoba and Saskatchewan down to Florida, and from the Atlantic coast west to Texas, although it is more common in the northern part of its range. It is considered threatened in the state of Arkansas, where it is also classified as a weed because it is a member of Cirsium. Although some species or Cirsium are invasive weeds detrimental to farming and grazing, C. muticum is not one of them, and is being eradicated unnecessarily. It serves as a larval host and a nectar source for certain species of butterflies and moths.