Musk Thistle Information

Musk Thistle-RosetteMusk Thistle-LeafMusk Thistle-Flowers

(Carduus nutans)

Tall, biennial, in some cases annual/winter annual

Distinguished from other thistles by:
            *Simple, not plumose pappus hairs
            *Nodding flower heads with spine-tipped green bracts

            *Grazed pastures
            *Oil fields
            *Idle pastures

            *May through June, sometimes into July
            *Individual plants can produce up to 100 flower heads

            *Terminal heads avg, 1,000 seeds, side branched avg. 125
            *Maturity and dispersal occur within 7-10 days of flowering
            *Germination rate of 1 year old seed is up to 90%
            *Germination rate is decreased in cold, moist soils
            *Optimum germination occurs only after adequate soil cover is established

Growth and reproduction:
            *First year: basal rosette may reach 3 ft. diameter
            *2nd year: plant bolts (vertical stem elongation), flowers, produces seed and dies
            *Reproduction is from seed only

            *Mowing must occur within 2 days of flowering to destroy seed viability
            *Hand digging must remove at least 2" of tap root when bolted, to kill entire plant and prevent
            *Clipping or pulling seed heads, bag and burn or bury
            *Herbicides: dicamba, metsulfuron, picloram or 2,4-D
            *Apply dicamba or 2,4-D ester in early spring, 2,4-D amine in late spring/early summer
             metsulfuron in summer up to bud break and picloram in fall.

            *Deep tap root competes aggressively for nutrients and water
            *Large rosette during first year shades and crowds out desirable plants
            *Livestock will not graze infested areas
            *Forage production can be reduced by as much as 50%