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LIST B <br /> Musk thistle - Carduus nutans <br /> A biennial thistle with very showy flowers producing up to 20,000 <br /> seeds per plant. Flower heads often bend over or nod, giving rise to <br /> the common name "nodding thistle." Reproduces only by seeds, which <br /> mature in June or July of the second year of growth. Often found in <br /> disturbed / overgrazed areas, but can invade various habitats. <br /> Identification: <br /> • Flowers: Purple, 1 .5 to 2.5 inches wide, nodding, solitary on stems; <br /> large triangular-shaped, spine-tipped bracts. <br /> • Leaves: Spiny, dark green, whitish margins, prominent midrib. <br /> • Stems: Leaves usually absent or very reduced below flower. <br /> Stem smooth below flower head. <br /> Control methods: <br /> Biological: <br /> The crown weevil, Trichosirocalus horridus, is available for control. <br /> Mechanical: <br /> Severing the root below the soil surface is a very effective control <br /> method. Mowing is most effective at full bloom, but flowering plant <br /> parts must be disposed of properly because seeds may still develop <br /> on cut plants. <br /> Chemical: <br /> *Picloram: Apply in spring to rosette. <br /> Metsulfuron: Apply in spring during rosette through very early <br /> flowering stages. <br /> Chlorsulfuron: Apply in spring during rosette through very early <br /> flowering stages. <br /> Aminopyralid: Apply in spring during rosette to early bolting <br /> stages, fall to rosettes. <br /> *Restricted-use chemical <br /> 40 <br />