374 



WEED FLORA OF IOWA 



Woolly Thistle (Cirsium canescens Nutt). 



Description. — Branching perennial, 2-4 ft. high, woolly through- 

 out, branches bearing single, medium-sized heads; stem angled, 

 white-woolly; leaves, radical, 8 in.-l ft. long, the division usually 

 2-lobed, prominently ribbed, ending in stout spines; stem leaves, 

 except the lower, 1-4 inches long, pinnatifid, the upper sessile, 

 slightly roughened, with a slight cottony down, the lower white- 

 woolly; heads iy 2 -2 in. high; bracts of the involucre somewhat 

 arachnoid; lower scales with a broad base, glutinous ridge, and 

 ending in a minutely serrated spine, inner scales long, attenuated, 

 tips straw-colored; flowers purple. 



Distribution. — This species is distributed from Mason City and 

 southwestern Minnesota, west to the Rocky mountains. It was 

 collected by Chas. A. Geyer in 1839 and described by Nuttall. The 



Fig. 219. Woolly Thistle (Cirsium canescens) . Common in western Iowa fields 



and roadsides. 

 (Photographed by Quade) 



