ROOTS AND ROOT-STOCKS OF WEEDS 



647 



Roots may be, classified according to their length of life, and this 

 is, perhaps, the most practical knowledge to possess concerning 

 weeds. Without this knowledge no intelligent or successful method 

 of eradication can be adopted. 

 . First we have the annuals or those which complete their growth 

 ajid mature their seed in one year. These plants produce an 

 enormous amount of seed, sometimes as high as 50,000 to a single 

 plant. The root system is simple, although it may extend to a con- 

 sidei*able distance horizontally. Such plants are easily destroyed 

 by cultivation unless they root from the joint as in the case of the 

 crab grass {Digit aria sanguinalis). 



Fig. 5.0 Z. 



Roots of Curled Dock (.Bumeas crispus). 

 (Photographed by Stevens.) 



Second are the winter annuals. These plants may begin, their 

 growth in the spring, in which case they become annuals. Many 

 of the seeds, however, germinate in the fall and throw up a rosette 



