398 



WEED FLORA OF IOWA 



FigTire 232A 



Figure 232B 



Fig. 232- a. Bristles on Prickly Lettuce (.integrata) . 



(Drawing by Charlotte M. King.) 



Fig. 232-B. Distribution of Prickly Lettuce. 



"Sheep and sometimes cattle will eat the young prickly lettuce, 

 and in some localities their services have been found very effective 

 in keeping it down, especially in recently cleared land where culti- 

 vation is impossible. Repeatedly mowing the plants as they first 

 begin to blossom will prevent seeding and eventually subdue them. 

 Thorough cultivation with a hoed crop, by means of which the 

 seed in the soil may be induced to germinate, will be found most 

 effective. The plowing should be shallow so as not to bury the 

 seeds tod deep. Under no circumstances should the mature seed- 

 bearing plants be plowed under, as that would only fill the soil 



Fig. 232-C. Distribution of Prickly Lettuce (Lactuca scariola). 



