VENTILATING ORCHID HOUSES. 



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the greatest mistake to leave a house of orchids closed until a certain time daily, for 

 such treatment results in failure. Ventilate always in accordance with the state of the 

 weather, but never leave a house shut up until some specified degree of temperature is 

 reached. Open the top ventilators slightly the first thing in the morning in summer, 

 before the sun reaches the house. This leads to a gradual rise in the temperature, much 

 more to the taste of the plant than an upward rush when the sun shines on a closed 

 house. It allows, too, of the shading being kept off the roof longer, and is a decided 

 advantage in every way. "Whenever it is possible, a little air should be left on the lower 

 ventilators at night, the houses always feeling much fresher in the morning than when 

 kept close. 



In dealing with cool houses in summer, it is sometimes an advantage after early ven- 

 tilation to keep them rather close by day, because the external air is often a good deal 

 hotter than the interior of the house should be. In this case heavy shading is of more 

 benefit than full ventilation ; but the house should be freely opened morning and evening, 

 and have more or less air left on at night, according to the state of the weather. 



Tropical houses are opened early, and closed as soon after midday as it is safe to 

 have the blinds up. The moisture from damping down rises and settles on the glass 

 when the house is closed, and prevents scorching of the plants. In early spring, when 

 cold winds are blowing, and the sun is bright at the same time, it is very difficult to 

 properly ventilate the houses. If kept too close, the temperature gets too high, while 

 cold draughts are caused by opening the ventilators. Open the sashes from the side 

 opposite to where the wind is blowing from, and shade a little more than usual, to pre- 

 vent too high a temperature. A little care in management is well repaid at such times, 

 and is more necessary then than in winter, when the majority of the plants are 

 resting, and not so easily injured. The aspect of the house, the position and the method 

 followed in ventilation, have all to be considered, so that it is impossible to give definite 

 instructions that will suit all cases. 



It may be noted that some of the finest dendrobiums, cattleyas, and other pseudo- 

 bulbous orchids in the country are grown in houses that are practically never closed 

 entirely at night, more or less air being always admitted, and fire-heat provided to keep 

 up the proper degree of heat. Amateurs, then, should note these few cardinal points 

 on ventilation, and shape their course accordingly. They will find that when a certain 

 plan has been tried and found effective, they are much surer of their ground than 

 when they follow blindly someone else's advice, whether good or bad. 



