NATIVE PLANTS IN ROCK-WALL 39 



planted out in a bed. The garden-nurtured plant 

 will be a foot and a half or two feet high, and its 

 large heavy head will be beaten about and twisted 

 by the wind till it has worked a funnel-shaped hole 

 in the ground, and is perhaps laid flat. Thrift, 

 that lovely little plant of rocky seashore and wind- 

 blown mountain top, is indispensable in all rock 

 and wall gardening, neat and well clothed all 

 through the year, and in summer thickly set with 

 its flower-heads of low-toned pink. It loves in 

 nature to grow along rocky cracks, sending its long 

 neck and root far down among the stones. There 

 is a garden form with bright green leaves and 

 darker coloured flowers, but, though it is un- 

 doubtedly a more showy plant it is scarcely an 

 improvement on the type ; much of the charm is 

 lost. 



The Red Valerian {Centranthus ruber) is a chalk- 

 loving plant ; it will grow in ordinary soil, but is 

 thankful for lime in some form. In this, the garden 

 form of deeper colour is a better plant than the type ; 

 the colour in this case being deepened to a good 

 crimson. Another British plant of the chalk that will 

 also be handsome in the rock-wall is the fine blue- 

 flowered Gromwell {Lithospcrmuni purpuro-cceruleuni) ; 

 it throws out long runners like a Periwinkle that 

 root at the tips. They seem to feel about over the 

 surface of the wall till they come to a joint where 

 they can root. 



Two of the British wild Pinks, namely, Dianthus 

 ccesius and D. deltoidcs, are among the best of plants 



