Santa Barbara County Weed Management Area
	Weed Alert!

Artichoke Thistle Asteraceae: Cynara cardunculus CDFA rated B; Cal-IPC rated A-1 The Santa Barbara County Weed Management Area advises landowners and ranchers to watch out for and prevent the establishment of artichoke thistle, a particularly nasty noxious weed, that occurs sporadically on the Gaviota Coast and elsewhere. Artichoke thistle is a spiny thistle that can grow to 5 to 6 feet tall. . Artichoke thistle is the wild form of the cultivated globe artichoke, Cynara scolymus. When grown from divisions of the perennial crown, globe artichoke will reliably produce the spineless, edible flowerhead and plant known to agriculture, but grown from seed it often reverts to a wild form, producing the inch-long spines on the phyllaries normally found on C. cardunculus. Gardeners are strongly encouraged to not allow globe artichokes in their garden to flower and set seed or to abandon their artichoke gardens. . Digging out a plant can control artichoke and artichoke thistle, but much of the taproot must be removed or new growth will develop from the cut surface. . Infestations of artichoke thistle can reduce forage production, limit wildlife, recreational, and livestock movement, and out-compete native vegetation. . Artichoke thistle reproduces by prodigious seed production. A mature plant can produce more than a dozen flowerheads with as many as 200 seeds per head. This species tends to produce mono-specific stands that can reach densities as high as 22,000 plants per acre. Plants can resprout from mowing or cutting. Seed banks are expected to live 5 years. . Seeds mostly fall and germinate near the parent plant. Wind, gravity, water can move seed to expand patch size. Seed can be moved by cattle, birds, and vehicles.   Foliar sprays of 2 percent glyphosate can achieve effective control especially when plants are sprayed at the bolting stage, which occurs in mid to late spring. Clopyralid is an effective herbicide, especially at the rosette stage, that is selective for Asteraceae and Fabaceae family species and has some pre-emergent effct. The infestation in these pictures was treated in May of 2005. For more information, visit: http://ucce.ucdavis.edu/datastore/detailreport.cfm?usernumber=38&surveynumber=182 http://www.cdfa.ca.gov/phpps/ipc/weedinfo/cynara.htm

*** This is a notice of a noxious weed of concern that occurs in Santa Barbara County. Remember - pesticides must be used in a manner consistent with the label directions. Permits may be required to use pesticides in agricultural areas and/or to conduct work in riparian areas.

 

 

May 25, 2005