WEEDS AND THEIR ERADICATION 227 



produces erect branching stems from one to three feet in height which are 

 somewhat roughened by short stiff hairs. 



The leaves are quite variable; the lower cnes are slender-stalked and 

 deeply pinnatifid, forming one large terminal lobe with two to four smaller 

 lateral lobes. 



The upper leaves are irregularly toothed, somewhat hairy and have 

 very short petioles; the lobes are not very pronounced, while the terminal 

 one is much narrower than the terminal lobe 

 of the lower leaves. 



The plant flowers from June to September 

 and mature seeds may be found as early as 

 August. The bright yellow, fragrant flowers 

 which are about one-half inch in diameter are 

 borne in elongated clusters at the end of the 

 stem and branches. 



The flowers begin to open at the bottom of 

 the cluster, which lengthens as the season 

 advances, and the pods form and empty so that 

 there may be emptied pods below and forming 

 pods above. One of the pods may contain 

 from four to twelve seeds. 



The round dark reddish-brown seeds are 

 about one-sixteenth of an inch in diameter. 

 They are a common impurity of grass and 

 clover seeds. 



Wild mustard grows in all kinds of grain 

 crops that are sown in the spring and usually 

 matures its seeds before the grain in which it 

 grows is ripe. Where spring grains are chiefly 

 grown the contest with this weed will be a 

 difficult one. 



Wild mustard is distributed by different 

 agencies. Some of the small seeds are carried 

 from place to place by the birds, but usually 

 the weed finds its way to new centers in grain seed. The threshing 

 machine is also a potent means of carrying it from farm to farm. 



It is further distributed over farms on which it grows by means of 

 manures. It is also very frequently distributed by spring floods; when 

 this is the case the farmer has a difficult job. 



Control. Wild mustard seed is a common impurity of small grain, 

 clover and alfalfa seed. The first step in its eradication is to avoid sowing 

 seed containing the pest. As the seeds are small, they are easily removed 

 from wheat, oats and barley by screening. Wild mustard is most common 

 in grain fields and generally disappears in grass and cultivated crops. 



1 Courtesy of The Pennsylvania Fanner. 



WILD MUSTARD 

 (Brassica arvensis). 1 



A Pod, natural size. 

 B Blossom, one-third natu- 

 ral size. 

 C Seed enlarged four times. 



