2i8 Diseases of Greenhouse Crops 



found to be weak and susceptible to disease. In first 

 pinching back the plants to encourage spreading, it 

 should be done in such a way that the plants will 

 branch some distance above the surface of the soil. 

 In other words, the farther the stems are from the 

 ground the more protected the plant is from disease. 

 When the plants are permanently set for the winter, 

 heavy watering should be avoided. Too much water 

 compacts the soil, excludes air, and retards normal 

 root development. As the plants become well es- 

 tablished, and especially during the hot days of Sep- 

 tember and October, as well as in the spring, they 

 should not be permitted to suffer from a lack of 

 water. This is especially true in raised benches with 

 the heating pipes directly underneath. In this case, 

 the surface soil may appear wet, yet the soil be- 

 neath may be as dry as possible. On the other hand 

 serious injury may occur from overwatering, espe- 

 cially in solid benches on cloudy days. The night 

 temperature of the carnation house should be about 

 fifty degrees F. At sixty degrees the plants will be 

 stimulated to slightly earlier blooming, but the 

 blooms will be small, and the plant subject to a 

 more rapid exhaustion. At a night temperature of 

 40 degrees F. blooming will undoubtedly be re- 

 tarded although the plants will be stockier and last 

 longer. The day temperature of the house should 

 be decided upon according to outside weather condi- 

 tions. On a clear day and when sufficient ventila- 

 tion is given, the temperature may run from 65 to 75 

 degrees F. 



