Bull Thistle (Cirsium Vulgare)

Bull thistle is a class C noxious weed in our county.

 Bull Thistle Rosette

Bull Thistle Rosette

Bull thistle displaces native vegetation. It can form dense thickets. Luckily, this plant isn’t as difficult to eliminate as Canada thistle because it does not spread by rhizomes.

Identification:

Bull thistle is a biennial plant. Rosette leaves are oblong with small spines at the tips of deep lobes. Stems on flowering plants are covered with fine white hair. Stem leaves are spiny and alternate. Each branch produces one or more 2” spiny purple flowers. The seeds are pale brown with dark streaks and a feathery plume growing from one end.

Control Methods:

·       Chemical

There are several herbicides that are effective on bull thistle. As always follow the label. For more information on herbicides and recommendations for control please see the Pacific Northwest Weed Management Handbook. Treatment is best used on first year rosettes.

·       Mechanical

Close cutting with a mower twice a season will prevent seed production and reduce the population over time. For more effective control cut the plants with a sharp shovel below the soil surface so that the plant does not re-sprout from stem left behind. Do this before the plant flowers. Tilling can be effective control for bull thistle.

·       Cultural/Biological

Goats and sheep have been used for grazing management of bull thistle. Cattle will not graze past the late bud stage. You will need to graze animals at least three successive years to reduce bull thistle population. There is one biocontrol agent. For more information on that visit:

http://invasives.wsu.edu/biological/urophorastylata.htm