4 THE CULTURE OF POT-PLANTS 



water instead of with air, the result being that the roots 

 decay. Soil in this state is called sour. Lime-water will 

 remove the sourness, but must not be used for such plants 

 as heaths, azaleas, and rhododendrons, for lime is most 

 injurious to them. Here, as always, prevention is better than 

 cure ; and though sufficient water should always be poured 

 into a pot to wet the whole of the soil and reach all the roots, 

 no more should afterwards be given until the soil is fairly 

 dry again, when the process should be repeated. Obviously, 

 the intervals between the waterings are very much shorter in 

 summer than in winter. Most plants are then making their 

 growth, and therefore using much moisture, while, owing 

 to the higher temperature, there is also much loss from 

 evaporation. 



It follows that to the common question : " How often 

 should I water my plants ? " no definite answer can be given. 

 There can be no fixed rule. It depends entirely on the 

 conditions — on the temperature, the weather, the soil (for 

 heavy soil holds moisture longer than light soil), on the 

 species, and even on the individual. A geranium, for instance, 

 will live under conditions of drought which would be fatal to 

 a hydrangea, and an aspidistra will thrive in moisture that 

 would kill a palm, while a plant which is making much 

 growth needs more than one which is making little. One 

 method of testing the condition of the soil is to tap the pot 

 sharply with the knuckles. If a clear ringing sound is 

 returned, water is required, the soil having shrunk away from 

 the pot ; if the sound is dull and muffled, the soil is not 

 sufficiently dry to have shrunk much, and may be regarded 

 as moist enough. The test, however, cannot always be relied 

 on. In the case of plants which should be potted very 

 firmly, such as chrysanthemums and palms, the soil, having 

 been rammed, does not, when dry, shrink sufficiently to affect 

 the sound, and experience is necessary to decide whether 

 more water is required or not. Generally speaking, it is 

 better in summer, during the growing period, to give too 

 much water rather than too little ; and in winter, during the 

 resting period, to give too Httle rather than too much. When 



