538 COMPOSITAE (COMPOSITE FAMILY) 



shaped base, all dark green, waxy-smooth, toothed with weak 

 spines. Heads in large corymbose clusters, deep yellow, nearly 

 two inches broad, the long rays five- 

 toothed, the bracts of the involucre 

 and the pedicels usually set with stiff, 

 glandular hairs, though in some locali- 

 ties a smooth and glaucous variety is 

 common. Achene brown, about an 

 eighth of an inch long, compressed, 

 with wrinkled lengthwise ridges, and 

 tufted with very copious, fine, white 

 pappus. (Fig. 371.) 



Means of control 



Short rotations of hoed crops, re- 

 ceiving very frequent, thorough, and 

 late tillage, are necessary in order to 

 clear the ground of this weed. It is 

 not harmed by any spray. Horse cul- 

 tivation serves only to break and spread 

 the rootstocks. Complete prevention 

 FIG. 371. Field Sow Thistle of food-assimilating green growth above 

 (Sonchus arvensis). x J. ground is the only sure remedy. 



COMMON SOW THISTLE 

 Sdnchus oleraceus, L. 



Other English names : Hare's Lettuce, Colewort, Milk Thistle. 



Introduced. Annual. Propagates by seeds. 



Time of bloom : June to September. 



Seed-time: July to October. 



Range: Throughout North America except the far North. 



Habitat: Fields, roadsides, waste places. 



In Europe this plant is used as a pot herb, as its specific name, 

 oleraceus, indicates, and is kept succulent by the constant pinching 

 out of its buds. It springs from a white taproot, well fringed with 

 feeding rootlets, the stem one to six feet tall, angled, branching, 



