PART L] CULTURAL 75 



the stones, especially if they contain cracks, may often be 



clothed with plants without any danger of overcrowding. I 

 have said little about choice of 



"STONE FOR ROCKERIES, 



though I have tried many kinds ; and of all I have tried, I pre- 

 fer the carboniferous limestone, common in North Wales, 

 Derbyshire, and the north of Lancashire. The loose blocks 

 of this which lie about the land are full of cracks and are 

 varied in shape. I carefully avoid the furrowed and smooth- 

 channelled surface slates of this stone often sold in London for 

 rockwork, but most unsuitable for growing plants ; I do not 

 speak of these, but detached solid blocks, abounding in deep 

 cracks and crevices. These crevices are the very place for 

 some of the choicest alpines. Paronychia shows its true 

 character in no other spot. Potentilla nitida flowers when 

 fixed in them, and there only. They are excellent for Phyteuma 

 comosum. The Spiderweb Houseleeks delight in them, and so 

 do some of the smaller Saxifrages. These are only a few of a 

 long list I might make, and things which grow in such tight 

 quarters never encroach much. The little Arenaria balearica, 

 which grows all over sandstone as close and in nearly as thin a 

 coat as paint upon wood, does not grow well upon limestone ; 

 but this plant does encroach, spreading over the surface of 

 small neighbours and smothering them. There are many 

 things, however some herbaceous, some shrubby and evergreen, 

 which do well only on condition of resting upon stone with 

 their leaves and branches. It is so with Pentstemon Scouleri, 

 and with that most charming dwarf shrub, Genista pilosa, which 

 rises hardly an inch off the stone, though it may cover several 

 square feet. I have said before that in planting, aspect must 

 be carefully considered. The best aspect for alpines is east, 

 and west is the worst ; but there is not a spot on any rockery 

 which may not be filled with a suitable tenant. Some of the 

 most beautiful flowers abhor, in the atmosphere of my garden, 

 even a glimpse of the sun. Eamondia pyrenaica is withered up 



