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Weeds Frequently get out of control because they are unnoticed. That is not the case, however, with Musk Thistle (Carduus nutans) infestations, which are marked by large reddish-purple flowers towering from plants measuring seven feet or more in height. Musk Thistle reduces forage quality and yields in infested hayfields and the plant's long, sharp spines limit the use of infested areas for grazing or recreation. The large reddish-purple flowers and deeply cut, dark green leaves aid in identification. Leaf bases extend around and beyond the stem, giving the plant a winged appearance.
weed

The flower heads "nod" as the plant reaches maturity, giving rise to the name "nodding thistle" in many areas.

Musk Thistle is classified as a biennial, although it often germinates in late summer, winters over as a rosette, and produces flowers and seeds the following summer. Musk Thistle is a native of Europe and Asia and most likely has been present in the eastern U.S. for 80 years. The infestation has now spread as far west as the Rocky Mountains. This weed may produce 50 to 100 heads per plant with 1,000 seeds per head, permitting rapid spread from seed. These seeds do not have a plume as do the seeds of Bull Thistle and Canada Thistle. Musk Thistle plants are easy to control with herbicides when treated in the rosette stage of growth. Herbicides should be applied in the spring before flowers stalks begin to form and elongate, or in the fall after new rosettes have emerged. Fall treatments should be applied before the ground freezes. Although the plant is easy to kill, control of an infestation requires controlling new seedlings which germinate both fall and spring, as well as control of rosettes already growing. A residual herbicide and repeat applications will be needed to eliminate infestations of Musk Thistle.

Effective control of Musk Thistle, as with most towering weeds, is best undertaken when the new weed is small. Occasionally, a mature thistle or two are noticed in a remote location and the observer should have no fear of approaching the weed with shovel in hand. Just cut the plant below the crown and leave it to die. If the thistle has NOT reached the mature flowering stage yet, thousands of seeds for next year's plants will be prevented. Mowing hay fields before seeds form in the thistle heads will reduce the thistle population. Good grazing practices which promote a vigorous grass stand will help prevent invasion of Musk Thistle into pastures.

A Seed Weevil has been effective in reducing seed production of Musk Thistle in some areas. These insects will slow the spread of the weed, but cannot eliminate an infestation. Plumeless thistle (Carduus acanthoides) is another biennial with similar growth habits and control recommendations as Musk Thistle. Biological controls have been less successful for Plumeless Thistle than for Musk Thistle. Plumeless Thistle is distinguished from Musk Thistle by its smaller flowers, which are born in dusters and are less nodding than flowers of Musk Thistle. Stems of Plumeless Thistle are branched and spiny, while Musk Thistle stems are barren. Leaves of Plumeless Thistle do not have the white midrib that is evident on Musk Thistle leaves.