Laserfiche WebLink
LIST B <br /> Scotch thistle - Onopordum acanthium <br /> Scotch thistle - Onopordum tauricum <br /> A non-native biennial forb that reproduces solely by seed. Can produce up <br /> to 14,000 seeds per plant. Due to spiny nature, Scotch thistle can act as a <br /> living barbed wire fence to livestock and can grow up to 12 feet tall. <br /> Invades overgrazed pastureland, roadsides, and irrigation ditches. <br /> Identification: <br /> • Flowers: 2 to 5 clusters, purple to dark red in color. <br /> • Leaves: Alternate, stalk-less, and spiny edged. <br /> • Stems: Numerous, branched, with broad, spiny wings. <br /> Lontrol methods: <br /> Biological: <br /> Urophora stylata, a fly predator, is used to help control this plant. The <br /> limited numbers do not allow for general redistribution. <br /> Mechanical: <br /> Any physical method that damages the root below the soil surface will <br /> kill the plant. Properly dispose of flowering cut plants, as seeds can <br /> mature and become viable. <br /> Chemical: <br /> *Picloram: Apply in spring or fall during the rosette stage. <br /> Aminopyralid: Apply in spring or fall during the rosette stage. <br /> Metsulfuron: Apply during rosette to early bolt stage of growth. <br /> *Restricted-use chemical <br /> 48 <br />