PLATE 34. 



PERENNIAL SOWTHISTLE, Sonchus arvcmh, L. 



Other English names : Field Sowthistle, Creeping Sowthistle, Corn 

 Sowthistle (in England), also sometimes incorrectly called the Russian 

 Thistle, which however is an entirely different plant belonging to the 

 Spinach family. 



(Noxious: Dom., Man., N.W.) 



Introduced. Perennial, very deep-rooted with large and vigorous run- 

 ning rootstocks. Stems 1 to 4 feet high, hollow, simple, with few leaves, 

 and branching at the top. Whole plant filled with a bitter milky juice. 

 Leaves 6 to 12 inches long, pointed, deeply cut, clasping the stem at their 

 base and edged with soft spines. Flowers bright yellow, li inches across, 

 in corymbs, closing in strong sunlight ; flower cup and flower stalk covered 

 in the common form with long glandular hairs. A perfectly smooth and 

 glaucous variety is common in parts of New Brunswick and also occurs at 

 I'ort Hope, Ontario. Seeds [Plate 54, fig. 22 — natural size and enlarged 8 

 times I brown, oblong, somewhat flattened, about | inch long, ridged both 

 lengthwise and across, bearing at the top a copious tuft of very white silky 

 hairs, which spTe:id in drj'iiig and enable the seed to bo carried long dis- 

 tances by the wind. 



Time of Floicering : June to August; seed ripe Julv to September. 



Propagation : Very rapid, by seeds and running rootstocks. 



Occurrence : Abundant in cultivated fields and along roadsides from the 

 Atlantic coast to Manitoba, where it is becoming very noticeable and giving 

 much anxiety in the Red River Valley. 



Injury: The Perennial Sowthistle, from its vigorous running root- 

 stocks and the large amount of seeds it matures, is one of the most aggressive 

 enemies of the Canadian farmer. Wherever it establishes itself, it causes 

 great loss both in reducing the yields of crops and on account of the great 

 difiiculty in eradicating it. 



Remedy: The adoption of a regular three-year or other short rotation 

 of crops is the only hope of clearing a farm infested with this weed. This 

 plan has been used with great success at Ottawa by Mr. Grisdale in cleaning 

 a field badly infested with Perennial Sowthistle. In the West summer- 

 fallowing must be done early and the land cultivated as often as necessary 

 to keep down the fresh growths as they appear. If still abundant on the 

 land, this should be plowed late in fall and seeded down the following year 

 or used for a crop of oats or barley, to be sown late after spring cultivation 

 and cut green for feed. When this plant first appears in new localities, the 

 Howering stems should be pulled by hand as soon as the blossoms show in a 

 growing crop so as to prevent the seed ripening. For land not under spring 

 crop, plough deeply in Juno and follow with rape, late roots or buckwheat. 

 \\ herever Perennial Sowthistle is common a short rotation of crops is a ne- 

 cfssity. 



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