PLANTING AND PROPAGATING ALPINES. 89 



slugs. Arabises are even more luxuriant that 

 Aubrietias. Bearing this in mind, the planter should 

 not put the Rock Cresses in positions near the top of 

 a rockery where they can spread downwards over 

 choice plants. It matters little how poor the soil 

 may be : a couple of years will see them broad, wide- 

 spread masses, and if other plants are not to suffer, and 

 slugs to enjoy a perfect covert, they must be dressed 

 back. It is safer to put them on lower sites, where 

 they can spread over the face of large stones and do no 

 harm to anything, or give them a separate section. 



The first thing, then, in putting in rock plants is 

 to take into account the habit and vigour of the plants. 

 A dense, low, clinging little plant like Hutchinsia 

 alpina should not be put a foot below the Snow-in- 

 summer, and both left to look after themselves. The 

 latter is a glorious plant, and makes the most 

 beautiful snowy masses, falling like a silvery cascade 

 over the rocks, but it is an even worse encroacher 

 than the Rock Cresses. One might fancy that it 

 dripped plants, for fresh ones come up all around and 

 beneath it, so that beautiful as it is in its snowy purity, 

 and with its exquisite silvery foliage, it actually becomes 

 almost a pest. The Rockfoils and Stonecrops (Sedums) 

 do not throw out the long, dependent streamers of 

 the luxuriant trio named, but many of the species 

 spread laterally into broad, close masses, which are 

 inimical to less virile kinds. The perennial Candy- 

 tufts {Iherises) may be quoted as another instance of 

 really beautiful and desirable plants which are apt 

 to prove too vigorous on small rockeries. 



