24 THE CULTURE OF POT-PLANTS 



may be more obscure. In that case a sick plant should be 

 turned out of its pot without disturbing the roots. If they 

 are not healthy, insects may perhaps be found among them, 

 or the soil may be excessively dry or excessively wet, too 

 hard or too loose, or unsuitable in some other way. If 

 another explanation must be sought, attention should be 

 directed to the position. Is it too sunny or too shady, too 

 hot or too cold, or is it draughty? As already pointed out, 

 one sure cause of disease in such plants as heaths, azaleas, 

 and rhododendrons is lime in the soil or in the water given 

 to them. 



There are three methods of getting rid of insects on pot- 

 plants — fumigation, vaporisation, and spraying or washing. 

 Fumigation consists in burning tobacco rag or paper. It 

 has been almost entirely superseded by vaporisation — the 

 heating by means of a lamp of various preparations sold for 

 the purpose — which is more cleanly, and quite as effective. 

 But when there are only a few plants, it is usual to resort to 

 spraying or washing. Soapy water will do quite well, but 

 there are many insecticides which are more powerful. All of 

 them should be washed off a few hours later with clean water, 

 and as they destroy only the insects, and not their eggs, they 

 should be used several times. The first spraying should be 

 done as soon as an insect is noticed. If it is delayed until 

 an attack is well advanced, it is very much more difficult to 

 get rid of the pests. 



Fungoid diseases are far more troublesome, for they 

 mostly develop inside the tissues, and only come to the 

 surface to perfect their fruit, just as mushrooms do. When 

 they become noticeable, the mischief is done. But even 

 if the parts already attacked cannot be saved, it is often 

 possible to confine an attack to those parts — to prevent its 

 spreading to other parts of the same plant and also to 

 different plants — and in time to stamp it out. In the 

 majority of cases, when the attack is a bad one, it is safest 

 to burn the affected plants in order to prevent the infection 

 of others. When it is less serious, the foliage should be 

 sprayed with a weak solution of permanganate of potash. 



