YELLOW STAR-THISTLE
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YELLOW STAR-THISTLE--Centaurea solstitialis L. Asteraceae--(Sunflower family)
Yellow starthistle is an annual, 2 to 3 feet tall, has rigid branching, winged stems covered with a cottony pubescence. Basal leaves are deeply lobed while upper leaves are entire and sharply pointed. Flower heads are yellow, located singly on ends of branches, and armed with sharp straw-colored thorns up to 3/4 inch long. Fruits from ray flowers are dark-colored without bristles, while fruits from disk flowers are lighter and have a tuft of white bristles.
Yellow starthistle, introduced from Europe, grows on various soil types and is usually introduced on roadsides and waste areas. "Chewing disease" results when horses are forced to eat the yellow starthistle.
A related species, Malta starthistle (C. melitensis L.) is similar to the yellow starthistle except the Malta starthistle has smaller seed heads having smaller spines which are branched at the base.
(Courtesy of Weeds of the West)
OTHER LINKS THAT HAVE INFORMATION ABOUT YELLOW STARTHISTLE
Plant Images from: USDA, NRCS. 2008. The PLANTS Database (http://plants.usda.gov, 19 March 2008). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.