Purple starthistle (Centaurea
calcitrapa L.) FamilyFamily: Compositae Description and Variation: Purple starthistle is an erect, branched, annual or biennial plant. The stems and leaves are covered with cobwebby hairs often becoming smooth with maturity. The lower leaves are deeply divided and the upper leaves are narrow and undivided. The rosette leaves are deeply divided with a circle of spines in the center. The flower is lavender to deep purple with spine-tipped bracts subtending the flower head. Economic Importance: Similar in some respects to yellow starthistle, this is an aggressive Centaurea, that is a major problem on annual rangelands in the San Francisco Bay area. Geographical Distribution: Infestations of purple starthistle are present in the North and Bay counties of California, and in Converse County, Wyoming. Purple starthistle was collected in Washington in 1989 from Asotin County (eastern Washington) and Island County (western Washington). A single plant was also identified in Adams county in 1990. Habitat: Purple starthistle occurs in grasslands; it tends to occur on sites more mesic than those occupied by yellow starthistle. When the two species occur together, purple starthistle grows on heavier bottomland soils. History: Purple starthistle is
native to Asia Minor from a region between the Black and Caspian seas. It was first
introduced into California in the early 20th century. It was reported from Ellensburg,
Washington in 1929. However, no additional reports were made for Washington until 1989,
when purple starthistle sites were found in Asotin and Island counties. The purple
starthistle introduction in Asotin County occurred on CRP land where grass seed
contaminated with purple starthistle was planted.
Growth and Development: Purple starthistle is a biennial that sometimes acts as an annual or a short-lived perennial. Reproduction: Purple starthistle reproduces by seeds. Response to Herbicides: Herbicides are most effective when applied in the spring to the sensitive rosette stage. Read and follow current herbicide labels and recommendations for control. Response to Cultural Methods: Grubbing or digging can be effective for small infestations of purple starthistle. Mowing is not effective. Biocontrol Potentials: No biological control program is currently being developed for purple starthistle. Reportedly, biotypes of Bangasternus, a seed head weevil, utilize purple starthistle in Europe. References: *Amme, David. Controlling Purple Starthistle, A Case Study. Unpublished Report. *Barbe, 1990. Purple Starthistle Detection map. State of California, Department of Food and Agriculture Detection Manual. *McMaster, V. 1989. Purple Starthistle found in Asotin County CRP. Nez Perce Soil and Water Conservation District Newsletter, September 1989, p.2. *Pratt, Dave. 1987. Purple Starthistle Control. Stock Talk, A Bi-monthly Newsletter. 3:6. Fairfield, CA *Roche’, C.T. and B.F. Roche’, Jr. 1990. Purple Starthistle (Centaurea calcitrapa L.) and Iberian Starthistle (Centaurea iberica Trev. ex Sprengel). PNW 350. Pacific Northwest Extension - Washington, Oregon, Idaho. *Roche', C.T. and B.F. Roche', Jr. 1993. Identifcation of Knapweeds and Starthistles in the Pacific Northwest. PNW 432. Pacific Northwest Extension - Washington, Oregon, Idaho. *Roche', C. and C.E. Hovanic. 1990. Washington Weeds: Purple starthistle. Washington Farmer Stockman 115(8):15. * Whitson, T. D., ed. 1987. Weeds and Poisonous Plants of Wyoming and Utah. Cooperative Extension Service, University of Wyoming. [Return to Class A Noxious Weeds]
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