bull thistle

Cirsium vulgare

   

Family: Asteraceae

Weed Class: C

Year Listed: 1988

Native to: Europe, Asia and Northern Africa

Toxic: not known to be

Other Legal Listings:

additional photos

 

   

Why is it a noxious weed?

Bull thistle may outcompete native plants and desirable wildlife and livestock forage plants. It can invade most any disturbed habitat and grow in dense thickets. Hay price may decline with the presence of bull thistle.

How would I identify it?

General Description: Bull thistle is a biennial herbaceous plant growing between 3 to 7 feet tall with one upright branched stem. It grows a rosette (cluster of radiating leaves at plant base) in its first year and blooms in its second year.

Flower Description: Flowerheads many, 1.5 to 2 inches in diameter. Bracts at base of flowerheads are spine-tipped. Flowers are purple or rarely white, blooming July through September.

Leaf Description: Leaves alternate and coarsely lobed. Each lobe has a spined tip. Leaf bases extend downward from the leaves along prominent ridges of the stem. Upper leaf surface is rough with bristle-like spines while the undersides are covered with white woolly hairs.

Stem Description: Stems are spiny-winged from leaf bases extending downward producing a winged ridge effect.

Fruit/Seed Description: Seeds are less than 0.16 inches (4 mm) long.

May be confused with:

How does it reproduce?

Bull thistle reproduces by seed and not by vegetative means.
 

Where does it grow?

Bull thistle colonizes primarily in disturbed areas such as pastures, roadsides, and ditch banks as well as in hayfields, disturbed prairies and logged mountain areas. Please click here to see a county level distribution map of bull thistle in Washington.
 

How do I control it?

Mechanical Control

Hand-pull and dispose of flowering plants in trash to prevent seed spread. Mowing can be effective, but make sure the plants do not flower. If cut too early before flowering, plants may re-sprout and flower again that season. Remove stems from site if plants are cut or pulled with flowers.

Biological Control

Bull thistle seed production is impacted by the seedhead gall fly, Urophora stylata. This gall fly’s larvae induce and feed on gall tissue in the developing bull thistle seedhead, reducing seed production up to 60%. Urophora stylata may significantly reduce seed production if bull thistle populations are sustained for many years. For more information about the biological control of bull thistle, please visit WSU Extension Integrated Weed Control Project

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.


 

For more information

 
Report on bull thistle from the book "Weed Control in Natural Areas in the Western United States"
See our Written Findings for more information about bull thistle (Cirsium vulgare).

Additional Photos


 
 

 


Bull thistle flower

 


Bull thistle growth

 


Bull thistle in flower

 


Bull thistle going to seed

 


Bull thistle leaf

 


Underside of leaf

 


Bull thistle winged stem

 


Bull thistle rosette

 


Bull thistle plants

 


flowerhead in bloom

 


plant habit

 


blooming flowerhead

    

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