MANAGEMENT OF GREENHOUSES 119 



combustion wastes coal, and too slow combustion may chill 

 the plants. A fireman should be given a boiler of sufficient 

 capacity to heat the houses to the required temperature 

 and the houses should also be well piped. The fireman's 

 duty is to keep the pipes sufficiently warm at all hours of 

 the day and night. The boilers should be kept clean or 

 there will be a pronounced loss of heat. Ashes should 

 never be allowed to accumulate underneath the boilers. 



93. Watering. Watering in greenhouses is an art, 

 the skillful operation of which few American gardeners 

 master. This duty requires much good judgment. Prob- 

 ably no one factor is more injurious to plants, and at the 

 same time more liable to occur, than overwatering. On 

 the other hand, neglect and drying out are also injurious. 

 Xo hard and fast rules can be given for the application of 

 water. The grower must learn from careful observation 

 when it should be applied and when withheld. Plants 

 in beds and benches are more liable to be overwatered 

 than are those in pots. This is especially true when it is 

 necessary to syringe frequently to keep insect pests in 

 check. The average workman fails to distinguish between 

 syringing and watering. In the first instance, it is pos- 

 sible by means of a fine spray to cover the foliage without 

 wetting the soil to any extent, while in watering the soil 

 is moistened without wetting the foliage. The novice finds 

 this difficult. Often the surface soil may be dry, while the 

 soil beneath is sufficiently moist for plant growth. This 

 is especially true after the surface soil has been recently 

 stirred, and extra applications of water would be injurious. 

 On the other hand, if the beds have been lightly watered 

 several times, it is quite possible that water has not pene- 

 trated deeply enough ito the soil to reach the basal root 

 system. It is, therefore, better to wet the bench so 



