WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Bull Thistle

(Cirsium vulgare)

Perennial Broadleaves

 

Bull Thistle

Habitat Characteristics

Bull thistle prefers a relatively rich, moist soil and is common in old fields. It is a weed of pastures, turf grass, landscapes, nurseries, orchards, and reduced-tillage agronomic crops.

 

Identification

The foliage of this biennial is covered with coarse to cobweb-like hairs. The young leaves are oval to oblong with a fringe of spines. The older leaves are longer and have spine tipped lobes. The young plants form a rosette. Older plants develop a tall (2-5 feet), erect, branched stem which hold flower heads singly. Flowers are pink to purple and the bases are covered in spines, in contrast to the spineless Canada thistle. Roots are fleshy in the first year and form a secondary fibrous root system.

 

Bull Thistle

Life History

This thistle reproduces only by wind dispersed seed, not by rhizomes like the Canada thistle. Flowers are present from June to October. Vegetative growth is seen in midsummer. The green seedling stage over-winters as a rosette and the stems elongate in the second year.

 

Thresholds and Management

Cultural Techniques

     - Regular mowing may control this weed if flowers are not allowed to form.

Chemical Techniques

     - See Herbicide Efficacy Table (pdf)

     - Bull Thistle is more susceptible to herbicides in rosette and actively growing stages.

 

Web References

USDA – NRCS Plant Profile, Bull Thistle http://plants.usda.gov/java/profile?symbol=CIVU&photoID=civu_005_ahp.jpg

B.C. Ministry of Agriculture and Lands, Bull Thistle
http://www.agf.gov.bc.ca/cropprot/weedguid/bullthis.htm

Invasive.org, The Source for Information and Images of Invasive & Exotic Species, Bull Thistle
http://www.invasive.org/browse/subject.cfm?sub=3393

Weeds B.C., Bull Thistle
http://www.weedsbc.ca/weed_desc/bull_thistle.html

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu