22 ROCK GARDENING FOR AMATEURS 



use them both to the best advantage. Firstly and chiefly 

 most alpine plants need a good depth of soil. One is 

 apt, in visiting a good rock garden, to get the impression 

 that the plants are growing in or on top of the rocks. 

 They may look as though they are they should, in fact, 

 do so but really their roots are deep down in cool and 

 moist crevices, or in fair depth of suitable soil. One has 

 only to read of the difficulties encountered by collectors 

 of alpine plants, owing to the great depth of the roots, 

 to realise that a deep root run must be provided. Soil, 

 then, is all important. Free drainage is not less so, 

 for a lack of well-drained soil is as bad as too little. If 

 the ground where the rock garden is to be built is fairly 

 light, and never very wet in winter, no drainage is 

 necessary. If, on the other hand, the land is heavy, 

 clayey stuff, proper drainage is most essential. As 

 the hills and mounds and headlands are built up, such 

 material as broken brick, pieces of flower-pot, pieces of 

 rock, leaf-soil, old potting soil, and coarse sand should 

 be very freely mixed in ; otherwise there will be great 

 danger of some of the plants deteriorating or dying in 

 winter. The necessity of incorporating such materials 

 in heavy soil cannot be too strongly emphasised, and, 

 further, when the actual planting of choice flowers is 

 carried out on such ground, holes not less than twelve 

 inches deep should be taken out, and the bottom filled 

 with drainage. Lucky, indeed, is the rock gardener 

 who has a light soil to deal with ; he is saved much tribu- 

 lation > He of the heavy soil, however, will have no 



