106 FRITZ BAHR'S COMMERCIAL FLORICULTURE 



nations, or, in fact, almost anything. From the daily waterings 

 given all Fall, there results an excess of moisture which, with 

 ventilators shut down, will transform the greenhouse into a wet 

 cellar over night, which a crack of air and a little fire would easily 

 prevent. As bad, only the other way about, is to fire heavily and 

 dry out the houses. The plants that have become used to moisture 

 in the atmosphere— or at least many of them— will object to this. 

 Wetting below the benches and the walks is usually necessary in 

 maintaining a certain degree of moisture. Plants differ, of course, 

 but watering the pots is not always enough. This, however, is 

 not to say that you cannot overdo things in this connection. 



Ventilation and Disease Control 



With a well-ventilated house, you can, to a great extent, check 

 stem rot in Carnations or hold in check mildew on Chrysanthemums. 

 You are not bothered with mildew during Summer because the plants 

 have more resistance and atmospheric conditions are not favorable 

 to it. The man who wets the fohage of the Chrysanthemums late 

 on an October day, invites trouble and the same in the case of 

 Carnations. The closer we get to Winter, the more careful we have 

 to be to avoid a stuffy atmosphere in the houses. While you 

 must provide a certain amount of moisture, at the same time 

 avoid wet foliage over night. The harder we fire the more im- 

 portant a part the hose plays in preventing a dry house. Heat itself, 

 whether from steam or hot water pipes, is heat pure and simple, 

 but if this heat is allowed to dry everything out in a greenhouse, 

 it will interfere with a healthy plant growth. 



Even in the houses kept at 50 or 40 deg. there should always 

 be attention paid to the moisture of the atmosphere as well as that 

 of the soil in which the plants are growing. 



In connection with the application of water, ventilation to a 

 great degree controls the atmospheric conditions of a greenhouse. 

 It also helps us to maintain under glass the desired temperature. 

 Good ventilation is such as will permit a circulation of air in a 

 house without letting cold draughts strike the plants. While some 

 plants are not as particular as others nor as sensitive, any plant 

 grown in a greenhouse and sheltered from the wind and weather to 

 which outdoor stock is subjected, will feel sudden changes of tem- 

 perature as well as of the air. It is of the greatest importance to 

 prevent any such variations. 



The larger a house, the easier it is to ventilate it properly and 

 the less chance there is of chilly air coming in contact with the 

 plants. The smaller the house, the more attention should be given 

 to opening and closing the ventilators. You cannot hope ever 



