498 



FIELD CROPS 



687. Weeds May Be Injurious to Man. Some weeds 

 are actually injurious to man. They may cause poisoning 

 from contact with them, as poison ivy, or from eating them or 

 their seeds. Wild parsnips are sometimes eaten for the 



cultivated kind, with 

 disastrous results. The 

 seeds of corn cockle 

 when ground with 

 wheat into flour are 

 poisonous, as are the 

 seeds of some other 

 weeds. 



BENEFITS FROM 

 WEEDS 



688. Uses. While 

 most weeds are inju- 

 rious, some may be of 

 value under certain 

 conditions. Leaves of 

 dandelions and young 

 shoots of pokeroot are 

 eaten as vegetables. 

 Many weeds furnish 

 pasture of more or less 

 value, though none of our domestic animals except sheep 

 ordinarily eat weeds when the more tender and nutritious 

 pasture plants are available. Sheep eat many kinds of weeds, 

 and are very often useful in keeping down these pests in 

 pastures and along fences. Weeds furnish a cover to land 

 which is not in crop, and may prevent loss of soil fertiHty 

 by leaching or by erosion. Deep-rooting weeds bring up 

 some plant food from the lower layers of the soil, and render 

 it available for crops which follow. They also open passages 

 for the movement of the soil moisture and make it easier for 



Figure 161. — Ragweed. 



