Weed of the Week

12-3-07

Bull thistle, Cirsium vulgare

 

Photographer: Cooper, G.A. [Image Details: format=TIF; size=5.9mb; width-height in pixels=2289 x 1526]

Forest and Kim Starr, U.S. geological Survey, Bugwood.org

 

Characteristics

Family: Asteracaea (Sunflower family)

Origin: Eurasia

Description:

• ·        Green/brownish Biennial with short, fleshy taproot

Stems:

• ·        2-5 feet tall with many spreading branches

Flowers:

• ·        Purple/pink flowers,1.5-2 inches wide clustered at the end of the branches

• ·        Involucre (area below the flower cluster) tapered and covered with spines

• ·        Flowering occurs July-September

Leaves:

• ·        Leaves rosette in first year

• ·        Pinnately lobed, hairy, prickly and cottony on underside of leaf

Fruits:

• ·        Topped by a circle of white hairs

Additional Information: Bull thistle is a highly competitive class B noxious weed. It is widely distributed throughout North America in pastures, roadsides and fields.

 

  

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