2S 



(ieclinc when jilanted in the same soil : therefore it is advisable to 

 change the soil occasionally. 



A good soil for greenhouse tomatoes consists of one-third 

 good loam, one-third pulverized sod, and one-third horse manure, 

 although in some cases, especially where a good, rich light loam 

 is available, the sod might be dispensed with, h^^equent and 

 liberal applications of horse manure, with decomposed sod ap- 

 plied occasionally will do much toward renovating a soil, but for 

 the best results it is necessary to change the soil every few years 

 or practice rotation. 



GENERAL CONCLUSIONS IN REGARD TO GREEN- 

 HOUSE DISEASES 



Anyone who has given the matter of greenhouse diseases con- 

 sideration is well aware that the more skill employed in growing 

 a crop the less likelihood there is of its becoming diseased. Even 

 a casual survey of some of the greenhouse establishments is suffi- 

 cient to demonstrate this fact. 



We kn.ow enough at the present time about the various kinds 

 of blights, rots, mildews, etc., common to greenhouse plants to 

 control them without syraying, and we know that if a cro]) is 

 managed along certain lines diseases will cause little trouble or 

 be entirely lacking. Spraying remedies, therefore, are not only 

 of little use, but, on the other hand, prove positively harmful, 

 since the gardener would not only be wasting his time on worth- 

 less methods, but his example would be putting a check on 

 progress. The expert grower knows the conditions required by 

 the plant and realizes the limitations of his crop. He knows 

 that there is a limit to the amount of forcing which can safely 

 be done, for too much forcing causes all sorts of troubles. He 

 realizes that disease is intimately associated with environment, 

 an.d that heat, light, moisture, etc., are very important factors 

 in growing crops. 



The plant, both in its chemical and physical characteristics, 

 is afifected by light, heat, electricity, soil antl air moisture and 

 biological relationships, and in the greenhouse by such factors 

 as ventilation, air space, size and quality of glass — in fact, the 

 simplest features connected with greenhouse construction. When 

 the conditions surrounding the plant are far from the optimum, 

 injury and even death result. A stimulus which may sometimes 

 prove beneficial may injure or cause the death of the organism 

 under other conditions, and it is only by meeting the optimum 

 conditions for stimulation and the normal requirements of the 

 plant that a perfect organism can be obtained. Therefore, 



