4 Diseases of Greenhouse Crops 



of his soil so as to make it ideal for his crops. By 

 combining the proper amounts of clay, silt, sand and 

 humus, he may give to the plants a most congenial 

 place to thrive in. To obtain such a result the gar- 

 dener must exercise his best judgment. By varying 

 the texture of the soil we may often influence the 

 plants unfavorably. Flowering plants may be made 

 to produce excessive foliage and few blossoms, while 

 others may be differently affected. 



Fertilizers 



Crops require certain food elements to make 

 growth possible at all, and they further require spe- 

 cific substances to enable them to accomplish definite 

 purposes. The carnation, for instance, requires pe- 

 culiar food elements to attain maximum growth. It 

 further requires special nutritive elements to enable 

 it to produce flowers and to avoid going altogether to 

 foliage. The four leading plant foods needed by 

 greenhouse crops are nitrogen, phosphorus, potassium 

 and lime. All the other plant food elements are 

 present in nearly all soils. 



The effect of nitrogen is to stimulate leaf and 

 stem growth, and to add green color. An overdose 

 of it, however, may result in soft plant tissue, and 

 thus retard fruiting. Acid phosphate stimulates root 

 growth, and an overdose of it encourages an excess 

 of root formation over foliage. Phosphorus also 

 stimulates earliness in fruiting. The effect of potas- 

 sium is to help the plant in assimilating other plant 



