78 ALPINE FLOWERS AND ROCK GARDENS. 



cannot have a really satisfactory construction without 

 a fairly good depth of soil and firmly-set stones. In a 

 sharply-pitched mound and with loose stones there 

 will be constant trouble from soil crumbling or being 

 washed down, sometimes bringing stones with them, and 

 leaving the plant with a draggly and hopeless aspect. 



The steeper the pitch the closer the stones should be 

 set. It might be thought that if the stones are packed 

 close together the interstices will be so small that 

 plants will be unable to establish themselves. This 

 is by no means the case. Such pretty things as Au- 

 brietias, Houstonia caerulea^ Snow-in-summer {Ceras- 

 tium)y Sempervivums, Saxifraga hypnoides, Corydalis, 

 Golden Drop (Onosma Tauricum), Thrift and Valerian 

 will be happy in very small crevices. Some of them, 

 indeed, may spread so fast as to need reduction. It 

 follows from this that if the amateur has a very steep 

 bank he may, if he likes, turn it into a rock garden 

 by facing it with stones packed close together, and 

 thrusting small bits of selected plants into the interstices. 

 The chances are that the result wiU astonish him con- 

 siderably, and that he will have a feature of such beauty 

 as will vie with the most attractive parts of the garden. 



These rock walls, built with loose stones, want a little 

 supervision after a protracted spell of heavy rain, as 

 occasionally one or two stones near the base will get 

 loose and slip out, endangering the stabiHty of those 

 near them. Such weak patches should be taken 

 in hand at once, and made good. A little earth should 

 be scraped out, and the stones rammed well in. 

 Whether stones be set in a wall, on a terrace, or in a 



