518 



COMPOSITAE (COMPOSITE FAMILY) 



ST. BARNABY'S THISTLE 

 Centaiirea solstitialis, L. 



Other English name: Yellow Star Thistle. 



Introduced. Annual. Propagates by seeds. 



Time of bloom: July to September. 



Seed-time: Late August to November. 



Range: Massachusetts to Ontario and Iowa, southward to the 



Carolinas and Arkansas ; also common on Pacific Coast. 

 Habitat: Fields, pastures, roadsides, and waste places. 



Seeds of this thistle have been noted by Alfalfa growers as a 

 common impurity in Alfalfa seed, especially of states of the Ohio 

 River Valley. They are so nearly the same weight of alfalfa 

 seed as to make removal difficult. When 

 in the soil the seeds have a vitality of 

 about three years, and are a most un- 

 desirable acquisition. 



Stem stout, rigid, erect, fifteen to thirty 

 inches tall, widely branched, gray with 

 loose woolly hair, and broadly winged by 

 the decurrent bases of the leaves ; these 

 are also gray -woolly, the lower ones pinnate 

 with terminal segment large (lyrate), and 

 lateral lobes narrow with wavy or sparsely 

 toothed edges ; upper leaves small, entire, 

 nearly linear, but all strongly decurrent. 

 Heads terminal, solitary, more than an 

 inch broad, bright yellow; involucre 

 broadly ovoid or nearly globular, the 

 inner row of its bracts ending in shining, 

 scarious tips ; the intermediate row armed 

 with rigid, yellow, divergent spines nearly 

 an inch long, with one or two shorter 

 ones at the base ; and the outermost row 

 having short, palmately branched spines. 

 Achenes light-colored, smooth, shining, 

 with soft, white pappus much longer than the achene. (Fig. 

 358.) 



FIG. 358. St. Bar- 

 naby's Thistle (Centaurea 

 solstitialis). X 1. 



