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.