228 ROCK GARDENING FOR AMATEURS 



are found wild in this country. Generally they are 

 easy to grow in light soil and a sunny position. The 

 Strawberry-like flowers, though individually fleeting, are 

 produced for weeks together, and are most attractive. 

 The varieties of Helianthemum vulgare, native of Europe, 

 including Britain, and North Africa, are chiefly grown, 

 and they range through many colours from white to red 

 and orange. There are numerous named sorts. Pro- 

 pagation is by cuttings taken towards the end of July. 



Houstonia. Houstonia caerulea is a dainty and tiny 

 rock-garden plant from North America, forming a low 

 cushion of minute evergreen leaves, from which in May 

 rise little pale blue flowers. It is the only one commonly 

 grown. Rubiaceae, to which belongs the Bouvardia, is 

 its natural order. It needs well-drained, light, loamy 

 soil and a position partially shaded by rock, so that it 

 may not become dried up in summer. It is increased by 

 division in September or by seeds. 



Hutchinsia. H. alpina, which alone is generally grown, 

 forms a neat evergreen carpet in sandy loam and a sheltered 

 spot, and in May bears tiny white flowers very freely. 

 It belongs to the Wallflower family (Cruciferae), and is 

 native of the European Alps. An increased stock is 

 obtained by dividing the tufts in late summer, or by 

 sowing seeds in spring. It is known also as Noccaea 

 alpina. 



Hypericum. The Hypericums, which belong to the 

 natural order Hypericineae, contain some of the most 

 charming of rock plants. Many of them are evergreen, 



