Identification
European Marsh Thistle
Cirsium palustre (L.) Scop.
Asteraceae (the Aster Family)
General appearance: Fibrous-rooted biennial or monocarpic perennial. Plants very spiny, with sparse to fairly dense (but not woolly) whitish hairs. Immature plants form a rosette (circle of leaves close to the ground). Flowering plants may reach 2 m (6.6 ft) or more tall.
Leaves: Rosette and lower stem leaves deeply lobed and toothed (pinnatified), with a strong midvein and a fairly short petiole, becoming shallowly lobed and sessile towards the top of the stem. The upper surface of the leaves have scattered hairs but no spines (but do have spines on margins). Leaves alternate on the stem.
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Stem: Winged, with numerous sharp spines along the wings. Ends of stems and branches somewhat nodding as they elongate. At anthesis, plants usually have a fairly straight, central stem with a few to many, short to rather long branches, bearing clusters of flowerheads at their tops.
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Flowers: Heads purple, relatively small, with involucre 1-2 mm (0.04-0.08 in) across, in clusters of a few to perhaps 12 or more, on short peduncles (stalks) at the ends of the branches. Flowers June through July.
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Seeds: Small, hard, elongated seeds about 3-4 mm (0.12-0.16 in) long, with a pappus of feathery bristles at the top.
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Habitat: Colonizes a variety of moist to wet habitats. Readily invades open, ruderal sites such as ditches, old fields, logging roads and right-of-ways. Also invades natural habitats, ranging from bogs, marshes, and wet meadows, to wet woodland edges and even interior woods.
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Sources: Tutin et al.(1976), Gleason and Cronquist (1991), Voss (1996).
Updated January 2006.
Visitor since March 17, 2006