494 



FIELD CROPS 



679. Annuals. An annual is a plant which makes all its 

 growth in a single season. The seed germinates in the spring 

 or summer, the plant produces blossoms and seeds the same 

 year, and then dies. The seeds of some annuals germinate 



in the fall and the 

 plants live over 

 winter, producing 

 their flowers and 

 seed the following 

 season, usually dur- 

 ing the spring and 

 early summer 

 months. These 

 plants are known 

 as winter annuals. 

 Corn is an example 

 of an ordinary an- 

 nual, and spring 

 wheat is another. 

 Winter wheat, on 

 the other hand, is 

 a winter annual. 

 Ragweed, crab- 

 grass, foxtail, and 

 mayweed are an- 

 nual weeds; shep- 

 herd's purse, corn 

 cockle, and cheat are usually winter annuals, though the 

 seed may not germinate till spring. Annuals spread only 

 by means of their seed. 



680. Biennials require two years to complete their 

 growth. The seeds germinate during the spring and summer 

 of the first year and the plants produce an extensive root sys- 

 tem, but do not develop much top growth. The following 

 spring they produce a large growth of top, blossom, ripen 



Figure 159. — Quack grass, or couch grass. 



