Weed of the Week

June 12th 2006

Canada Thistle, Cirsium arvense (L.) Scop.

                       

 

Characteristics

Family: Asteraceae (Sunflower)

Origin: Europe

Description:

• Deep rooted Perennial
• Reproduces by seed and root stock

Stems:

• Erect, hollow, smooth, slightly hairy
• 1-5 feet tall, simple and branched at the top

Flowers:

• Pink to purple colored flowers
• Bloom occurs June-August
• Multiple flowers are small and compact, 3/4" in diameter
• Seeds are 1/8 inch long and are tufted, like dandelion seeds and are easily distributed by wind

Leaves:

• Attached close to the stem
• Dark green in color
• Covered with sharp spines

Location:

    Canada Thistle is a very common and problematic weed.  The root system is often extensive.  It propagates quickly and is able to exist in many different ecosystems.  It is distributed along roadways, forests, lawns, rangeland, and riparian areas from 4,000 to 9,500 feet in elevation.

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