CHAPTER II. 



KINDS OF WEEDS AS TO DURATION 



V 



Weeds may be grouped with reference to their duration 

 under the following classes : Annual, biennial, and peren- 

 nial. An annual plant is one which germinates from seed 

 in the spring, produces flowers and seed the same season, 

 after the accomplishment of which it usually dies. Ex- 

 amples of annual weeds are foxtail, ragweed, and smart- 

 weed. The members of this class 1 vary greatly. Some an- 

 nuals approach biennial in habit 

 and are called winter annuals. 



Seeds of winter annuals ger- 

 minate in the fall and produce a 

 good growth until checked by 

 frost. In the succeeding spring 

 they make rapid growth, mature 

 fruit, and die. Examples of win- 

 ter annuals are speedwell, shep- 

 herd's purse, and chickweed. 



The biennial plant, during the Fig> x> c ' anada thistle 



first season, produces vegetative seed; a common source of 

 growth only, this often consist- J5 re *^ n K the weecL < c - 



r f i i M. K.mg.) 



mg of a rosette of leaves closie to 



the ground. In the second season, a flower stem is pro- 

 duced. Examples of biennial weeds are bull thistle, mul- 

 lein, burdock, parsnip and carrot. Biennial weeds do not 

 appear when the ground has been properly plowed. 



The perennial plant has a natural existence of more 

 than two years. These plants produce stems, and roots 

 which send up flower stalks year after year. Examples 

 of this class are morning glory, milkweed, horse-nettle, 

 and horse-radish. 



