Weed of the Week

3-31-08

Plumeless Thistle, Carduus acanthoides

                  

Photo credits: Todd Pfeiffer, Klamath County Weed Control (Flower), Richard Old, XID Services, Inc. (Whole Plant)

 Characteristics:

Family: Asteraceae (Sunflower family)

Origin: Eurasia

Description:

• Winter annual of biennial herb

• Fleshy stout taproot

• Rarely flowers the first year

Stems:

• 1-4 feet in height, widely branching with spiny wings

Flowers:

• Pink to purple 1-2 inches across with lower bracts spiny in appearance

• Flowers May to July

• Flower heads are at the ends of the branches and can be clustered two to five

Leaves:

• Basal leaves are spiny and lobed approximately 4-8 inches in length

• Stem leaves are alternate without a stalk and blend into the stem

Fruit:

• Seeds are small with a plume of white hair like fibers

Additional information:

Abundant in pastures, steam valleys, fields and roadsides.  It is common in Colorado, Idaho and Wyoming and has the potential to become a serious problem in the future.

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