Musk Thistle

  • Musk Thistle

    Musk thistle is a biennial which means it only lives for two years. The first year it presents itself as a rosette at ground level. The second year it bolts and sends up a tall flowering stalk with many purple flower heads. Whenever it is clipped or mowed it quickly regrows new flowers.

    Growth Habit – This weed is a biennial, which means that it appears only as a rosette the first year and as a flowering plant the second year. At maturity, it grows up to 7 feet tall.

    Flower – This thistle is also known as Nodding Thistle because the 1 to 3″ purple flowers found at the end of stems, tend to droop when mature. The bracts below the flower head are reflexed back.

    Leaves/Stems – Both the leaves and the stems are prickly. Leaves are usually edged with a grey or silver color.

    Reproduction – It does not have a massive root system and multiplies only by seed. Each plant can produce up to 10,000 seeds that are then dispersed by the wind.

    Management –

    • Rosette Stage:
        • Pull, dig or spray all rosettes when it first appears
        • Spray with a herbicide
    • Prior to Flowering:
        • Pull, dig or spray all bolting plants including roots
    • Once flowering has begun:
        • Remove (clip) ALL seed heads and place in garbage bags for disposal in the GVM compactor
        • There is a high probability that herbicides will be ineffective. Remember musk thistle will die after flowering anyway

    Caution –

    • This thistle can be confused with the native Colorado Thistle, which has white flowers and blue-green foliage.
    • This Colorado Thistle is NOT considered to be a noxious weed and need not be eradicated.