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 seryes only to break and spread 
| ‘the rootstocks. Complete prevention 
Fic. 371. — Field Sow Thistle Of food-assimilating green growth above 
(Sonchus arvensis). X%. ground is the only sure remedy. 
COMMON SOW THISTLE 
Sénchus olerdceus, 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, 
