musk thistle

Carduus nutans

   

Family: Asteraceae

Other common names: nodding thistle

Weed Class: B

Year Listed: 1988

Native to: Europe and Asia

Toxic: not known to be

Other Legal Listings: WA Quarantine list, WAC 16-750

additional photos

 

   

Why is it a noxious weed?

It invades pastures and fields, crowding out desirable forage plants. Livestock will not graze in areas heavily infested with must thistle, thus decreasing available pasture. It hinders stream bank access, and is problematic in grain fields.

How would I identify it?

General Description: Musk thistle is typically a biennial though may be a winter annual. It can grow up to 7 feet tall.

Flower Description: Flowerheads mostly solitary and large, up to 3.1 inches across and nodding. Bracts under flowerheads are broad, some reflexed with a spiny tip. Each plant can have 50 to 100 flower heads.

Leaf Description: Leaves are alternate, deeply lobed, spiny and may have some hairs on the underside leaf veins.

Stem Description: Stems have spiny wings.

Fruit/Seed Description: Seeds (achenes) are smooth and hairless.

May be confused with:

How does it reproduce?

Musk thistle reproduces by seed.
 

Where does it grow?

Musk thistle grows in pastures, rangeland, native meadows, roadsides, forests, stream banks, and occasionally grain fields. Please click here to see a county level distribution map of musk thistle in Washington.
 

How do I control it?

General Control Strategy

Establishing a dense, well-maintained pasture is effective in preventing a musk thistle infestation.

Mechanical Control

Musk thistle can be dug or grubbed out.

Cultural Control

Cultivation in cropland will kill young musk thistle seedlings.

Biological Control

A seed eating weevil, Rhinocyllus conicus, is quite effective in reducing seed output.

Herbicide Control

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


 

For more information

 
See our Written Findings for more information about musk thistle (Carduus nutans).

Additional Photos


 
 

 


musk thistle infestation

 


flowerheads with bracts

 


flowerheads blooming and going to seed

 


Musk thistle flowerheads

 


Musk thistle flowerhead in bloom

 


Musk thistle flowerhead bracts

 


Musk thistle plants

 


Musk thistle going to seed

 


plant with developing flowerheads

 


developing flowerhead with broad, pointed bracts

 


young plant

 


plant with developing flowerheads

    

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