A single flower head may produce 1,200 seeds and a single plant up to 120,000 seeds
Seed may remain viable in the soil for over ten years
Unpalatable to wildlife and livestock
Can grow to 6 feet
Musk thistle is a non-native biennial forb that reproduces solely by seed.
Stems are upright, green-grayish, and can grow to 6 feet tall with spiny wings .
Leaves The leaves are spiny, waxy, and dark green in color with a light green midrib.
Flowers are purple, large in size (1.5 to 3 inches in diameter), nodding, and terminal.
Seed/Fruit can produce thousands of straw-colored seeds adorned with plume-like bristles.
Musk thistle grows from sea level to about 8,000 ft elevation, in neutral to acidic soils. It invades open
natural areas such as meadows, prairies, and grassy balds. It spreads rapidly in areas subjected to
frequent natural disturbance events such as landslides and flooding but does not grow well in
excessively wet, dry or shady conditions.
Because musk thistle is unpalatable to wildlife and livestock, selective grazing leads to severe
degradation of native meadows and grasslands as wildlife focus their foraging on native plants, giving
musk thistle a competitive advantage
Mechanical: Musk thistle will not tolerate tillage and can be removed easily by severing its root below
ground with a shovel or hoe. Mowing can effectively reduce seed output if plants are cut when the
terminal head is in the late-flowering stage. Gather and burn mowed debris to destroy any seed that has
Apply herbicides such as Picloram, Aminopyralid, Dicamba, or 2,4-D to musk thistle rosettes
in spring or fall. Apply chlorsulfuron up to the early flower growth stage.
Two weevils have been introduced from Europe and released in the United States as a
biological control for musk thistle, the thistlehead-feeding weevil (Rhinocyllus conicus) and the rosette
weevil (Trichosirocalus horridus). These weevils have been released in a number of western states with
some notable successes achieved. However, recent observations of unintentional and unanticipated
impacts of the thistlehead-feeding weevil to native thistles, including some rare species, has raised a
concern about its continued use, at least in the western U.S.