MULCHING, SHADING, AND WATERING. 249 



cisterns, as it is well aerated aud abounds in ammonia 

 and fertilizing gases. If spring or well water must be 

 used, add a very little guano, say a pound or two to 

 twenty gallons of water, giving the smaller quantity to 

 delicate plants, and the larger to gross feeders, and before 

 using let it stand a few hours. Manure from the hen roost 

 in double quantity may be substituted for guano. For 

 sprinkling the foliage, pure water is better. 



The temperature of water, too, must be regarded. The 

 good effects of bottom heat in hot-beds, or of artificial 

 heat in greenhouses, are often entirely counteracted, and 

 plant growth brought to a stand by watering with cold 

 water. It is not only the lowering of the temperature of 

 the roots of plants, but the suddenness of the change that 

 is injurious and often fatal. Water should always be 

 applied a few degrees warmer than the soil, that growth 

 may be promoted and not checked. 



As to the time of day at which water should be given, 

 unless applied quite freely, it does little good iu the heat 

 of a summer's day, as the hot atmosphere drinks up the 

 moisture before the plant can imbibe it. The effect of 

 rain can be best secured by watering just at night, when 

 the falling dew will, in some measure, prevent evapora- 

 tion from the plants, and they will be fully refreshed 

 during the night. But in the spring of the year, to water 

 in the evening in dry weather darkens the soil, and, there- 

 fore, increases radiation. Evaporation is also greatly in- 

 creased; the temperature sinks rapidly, the plants are 

 chilled, if not frozen, and make less growth than if not 

 watered at all. So, also, in autumn, for the same reason. 

 In both spring and autumn, therefore, water only in the 

 morning, and the heat of the soil will not be materially 

 lowered, the sun's rays communicating fresh warmth. 



It should be the great object of the gardener to avoid 

 the necessity of watering, by shading the earth or the 



