WEEDS OF ARABLE LAND 101 



may escape notice and reach the flowering stage. 

 The latter may be most easily effected after rain has 

 softened the ground. Surface cultivation in spring, 

 so frequently recommended in these pages against 

 annual weeds, will destroy many seedlings. In root 

 crops as well as in garden cultivation the regular and 

 thorough hoeing which is usual suffices to keep down 

 the weed. 



The Perennial or Corn Sow Thistle (Sonchus arvensis 

 L.) is a much more troublesome weed than the species 

 mentioned above, since it is propagated both by seeds 

 and by a creeping rootstock. The stem is 2 to 4 feet 

 high, but little if at all branched, and tubular and 

 angular ; the leaves are wavy and toothed, almost 

 spinous, but very variable ; the heads of the yellow 

 flowers are somewhat hairy, and i to 2 inches in dia- 

 meter. This weed is spread by seed as in the case 

 of S. oleraceits, but it does not bloom so early, not 

 until August and September, when the annual species 

 is scattering its seeds. It is a vigorous grower, and 

 is stated to be one of the most aggressive enemies 

 of the Canadian farmer. 



The Corn Sow Thistle occurs on all soils, and often 

 causes great loss. It must not only be prevented from 

 seeding, but the creeping rootstock must be destroyed. 

 Both may be accomplished as in the case of the 

 Creeping Thistle (p. 87), but rather more easily, 

 S. arvensis appearing to be less resistant to tillage 

 operations than Cnicus arvensis. 



A short rotation, with the free use of the hoe in 

 two or three root crops, kills it, and it is destroyed 

 by laying down the field to grass for a few years. 



In Canada buckwheat appears to be a useful ally 

 in keeping down this weed, and a writer has lately 

 described the plan followed in order to keep down the 



