Musk Thistle Information
(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
Habitat:
*Roadsides
*Grazed pastures
*Oil fields
*Idle pastures
*Rangeland
Flowers:
*Monoecious
*May through June, sometimes into July
*Individual plants can produce up to 100 flower heads
Seeds:
*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
Management:
*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
re-sprouting
*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.
Threats:
*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%