THE WALL GARDEN 119 



most difficult to keep in the rock garden 

 proper. Nor is the reason difficult to find, 

 for in the wall there is the perfect drainage, 

 and there is not the same risk of loss 

 from excessive damp, which more often than 

 anything else proves fatal to alpines in this 

 country. The chief and only difficulty con- 

 nected with wall gardening is that of establish- 

 ing the plants. If planted after the wall is 

 finished, they can only be very small and 

 therefore young ; for they will have to be 

 inserted in the narrow crevices between the 

 stones, often no easy task to accomplish, and, 

 having to be so young, they are more liable to 

 be affected by the vicissitudes of temperature 

 than would the older and better-matured 

 plants. For these reasons it will be found 

 advisable, when at all practicable, to plant as 

 the building proceeds. Larger and stronger 

 plants can then be used, and their roots can be 

 properly spread out and encouraged to pene- 

 trate into the cooler mass of soil behind the 

 stones forming the wall. This will render 

 them far less liable to suffer from drought. 

 Although this method of building the retain- 



