 Marsh Plume Thistle
Cirsium palustre
Family: Asteraceae
Description and Life Cycle:
A fibrous rooted, biennial herb growing 0.2-2.0 m tall. Stems are erect, slender, ribbed; sometimes with ascending branches; strongly spiny-winged from the winged leaf bases. Basal and lower stem leaves are narrowly elliptic. Middle stem leaves and reduced upper ones are lance shaped and lobed to about ½ the width of the leaf, with narrow, spine-tipped segments and winged bases. Leaves are nearly hairless to lightly, soft hairy on the upper surface, and lightly to densely long-hairy below. Flower heads are disc-shaped, compact purple clusters terminating the stem or at the ends of branches. Bracts are cobwebby and often sticky. Seeds are 2.5-3.5 mm long, 1 mm wide, straw-coloured to almost white; with a fringe of hairs 9-10 mm long.
Seeds germinate in early spring (can also germinate as late as October) and rosettes begin vigorous growth, filling in the surrounding area by summer. Their numerous leaves form disks that eliminate other species by pressure and shading. Flowering and fruiting occurs the following year, and mature individuals die.
Note: there could be confusion in identifying marsh thistle from bull thistle.
 Biological Control Agents
References
MFR staff observations and comments
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