110 Elementary Principles of Agriculture 



served. Plants suffering from the attacks of insects 

 or fungi are not fruitful because they are imperfectly 

 nourished. 



(b) Provide the roots with the proper amounts of 

 phosphoric acid, potash, and nitrogen. An excess of nitro- 

 gen tends to favor growth of leaves and shoots at the 

 expense of flowers. Phosphorus and potash favor the 

 formation of flowers and the full development of the 

 fruit and seeds. 



(c) Check any unusual or unnecessary growth of the 

 stems by withholding excessive supplies of water. This 

 check to the growth naturally results when the warm 

 weather of the summer sets in. Where the plants are 

 grown under glass it is often possible to regulate the time 

 of flowering by controlling the water supply. 



161. Fruiting in Perennial Plants is sometimes so 

 excessive that they are greatly damaged. Fruit trees 

 "overbear" to such an extent that they exhaust all the 

 reserve food, and the flower buds do not develop for the 

 succeeding crop. This gives rise to the habit of producing 

 a crop every other year, noticed in apples and peaches. 



162. Sterile Plants, or other plants that are kept from 

 fruiting, tend to become perennial. If the formation of 

 fruits is prevented or removed while young, they con- 

 tinue to grow and form new flowers. In this way, sweet 

 peas, nasturtiums, and other plants grown for their 

 flowers, have their blooming period prolonged. Garden 

 plants of which the fruit is gathered immature, as beans, 

 cucumbers and okra, grow much longer than they would 

 if the first fruits formed were allowed to mature and 

 exhaust the plant. Clover, grown so extensively in the 

 North and in some southern states, is a biennial ; though, 

 if prevented from fruiting, it becomes a perennial. 



