The Perennial Sow Thistle. 



(Sonchus arvensis, L.) 



This is by all means the worst weed in the Province of Ontario at 

 the present time. It is found in almost every county, and upon almost 

 every farm. So rapidly and so persistently is it spreading- that in some 

 parts of the Province it threatens to entirely over-run the fields and drive 

 out the farmer. In spite, however, of its wide dispersal there are many 

 who are not able to recognize this pest and who mistake it for its two 

 comparatively harmless cousins, the Common Annual Sow Thistle and 

 the Spiny Annual S'ow Thistle. This should not be the case, as it is a 

 very conspicuous weed, and differs markedly from the other two species. 

 The Perennial Sow Thistle grows freely on a great variety of soils, but 

 is especially troublesome on rich, low, damp land. It appears the first 

 year in a field in scattered patches consisting of young plants, each plant 

 made up of a rosette of leaves lying close to the ground, and thus, when 

 numerous, they completely cover it. These young plants have but short 

 underground root stocks, and are comparatively easy to destroy. The 

 second year a large stem bearing numerous leaves and flowers is pro- 

 duced and the rootstocks grow long and send up quantities of new shoots. 

 Once established in this manner, it is no easy task to destroy this pest. 



Description: The Perennial Sow Thistle (Sonchus arvensis) is a 

 tall, coarse growing perennial weed with deep roots and numerous thick, 

 underground stems or rootstocks, commonly spoken of as "roots." Upon 

 these at intervals of a few inches are borne buds which develop into new 

 plants. The stem is smooth and hollow and the whole plant is filled with 

 a bitter milky juice. The leaves are pointed, 4 to 12 inches long, deeply 

 cut with the segments pointed backwards (runcinate), slightly prickly. 

 The flowers, or more correctly speaking, the heads of flowers are about 

 1 to \\ inches across, and bright orange in color. The involucre, or, as 

 it is commonly called, the flower cup. and the peduncles or flower stems 

 are covered with distinct, yellow glandular bristles. The seeds are dark 

 reddish-brown in color, about \ of an inch long, somewhat spindle shaped 

 with blunt ends, and each surface bears a number of very deeply wrinkled, 

 longitudinal ribs. Each seed bears at the top a tuft of white silky hairs 

 (pappus) which, when dry, acts as a parachute and enables the seed to be 

 borne long distances by the wind. 



Points of Distinction Between the Perennial Sow Thistle and the 



Annual Sow Thistles. 



1. The Perennial Sow Thistle is a taller, coarser growing plant than 

 either of the other two Sow Thistles. 



2. The Perennial S'ow Thistle has numerous underground rootstocks 

 while the annual species have only fibrous roots. (See illustrations.) 



