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L. N. May

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Calcareous shores, sedge meadows, fens; swamps of cedar, tamarack, and other conifers (less often hardwoods); moist ground along rivers and streams.

The flowers are a deep rose-purple; combined with the relatively unarmed stem, they make this species unusually attractive as thistles go. White-flowered plants [f. lactiflorum Fernald] have been collected in Keweenaw, Livingston, and Oakland Cos. The phyllaries are less acute (even obtuse or blunt) compared with our other small-headed thistles (C. arvense and C. palustre, both introduced, weedy species), which have pale pink-purple flowers. Occasionally the leaves are lightly tomentose beneath, but not enough so to hide completely the green surface of the blade.

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