3. The leaves of the Common Annual Sow Thistle are deeply cut 

 and lobed and scarcely spiny. The leaves of the Spiny Annual Sow Thistle 

 are almost entire, very prickly and often decidedly waxy. The leaves of 

 the Perennial Sow Thistle are deeply cut, but not lobed and slightly 

 prickly. (See illustrations.) 



4. The "flowers" of the Perennial are brig-ht orange in color and 

 about 1$ inches across, while the flowers of the Annuals are pale yellow 

 and less than \ inch in diameter. 



5. The "flower-cups" (involucres) and "flower stems" (peduncles) of 

 the Perennial Sow Thistle are conspicuously covered with yellow glandu- 

 lar bristles while those of the annual species are nearly smooth. 



6. The seeds of the three species also differ as to shape and mark- 

 ings as shown by the accompanying illustrations. 



How the Perennial Sow Thistle is Spread. 



The Perennial Sow Thistle is being rapidly and widely spread by 

 means of its numerous seeds, which are blown far and wide by the wind, 

 and to some extent by its abundant underground rootstocks which, with 

 remarkable rapidity, spread through a field sending up new shoots which 

 soon entirely cover the ground and choke out all other vegetation. The 

 rootstocks when broken up are often carried from field to field by harrow 

 or cultivator. It has been estimated that an average plant produces 2,000 

 seeds. There are thousands of these plants going to seed on neglected 

 farms, on road sides and in fence corners. Many more mature plants 

 are harvested with the grain and their millions of seeds scattered at 

 threshing times. Is it to be wondered that the Perennial Sow Thistle 

 is becoming such a serious pest in Ontario? 



Methods of Eradication. 



These are discussed under the headings of General Suggestions, 

 General Methods and Detailed Methods. 



General Suggestions. 



1. Bear in mind that a few patches of Perennial Sow Thistle, if 

 allowed to mature, may seed down a whole neighborhood. Therefore, 

 take every precaution to prevent the seeding of patches in meadows, 

 grain fields, fence corners, and on the road side. 



2. Watch for the first two or three patches in the field and destroy 

 them before the pest becomes established. 



3. Be careful not to harrow or cultivate through patches and drag 

 the underground rootstocks all over the field. 



4. The Perennial Sow Thistle thrives most luxuriantly on rather low, 

 damp land. Underdrawing- therefore will help to control it. 



5. Sheep are fond of this weed, and, if turned on a field after har- 

 vest, will prevent its seeding and by their close cropping weaken the 

 underground rootstocks. 



