98 ROCK GARDENING FOR AMATEURS 



crevices are to be planted the best plan is to insert the 

 plants as the building proceeds, otherwise it is difficult 

 to get the roots far enough back. Presuming the planting 

 to be finished, it remains only so to treat the concrete 

 that it bears some resemblance to natural rock. The 

 materials needed are of the simplest Portland cement, 

 sand and water. Suitable proportions for mixing are 

 half cement and half sand, or perhaps rather more sand 

 than cement. Sufficient water is used to bring the mixture 

 to the consistency of paste, otherwise it does not stick 

 well on the perpendicular face of the stone. A mason's 

 trowel is the best tool with which to put on the cement. 

 Immediately one of the slabs is finished, sand should 

 be scattered very freely all over it ; in fact, it is necessary 

 to throw the sand forcibly so that it may become firmly 

 embedded in the cement. When cement and sand are 

 dry a very fair substitute for a sandstone rock results. 

 Care should be taken to make the surface as rough and 

 irregular as possible. This is easily achieved by forming 

 small ridges in the moist surface by means of the trowel, 

 and by disguising the corners and edges by using an 

 increased quantity of cement and sand. 



The vertical fissures should also be filled with the 

 cement and sand mixture, still further to assist in the 

 delusion. It is not wise to close the horizontal fissures 

 on the top of the " rock," otherwise rain will not be 

 able to penetrate freely to the roots below, but they will 

 soon be hidden by various plants. Such a method of 

 providing a substitute for real stone may be, and probably 



