ROCK GARDENS, NATURAL AND ARTIFICIAL. 



163 



KOCK GARDENS, NATURAL AND ARTIFICIAL. 

 By R. Lloyd Praegek, B.E., B.A., M.R.I.A. 



(Substance of a lecture delivered March 22, 1909). 



Of late years the cultivation of alpines and rock-plants has been increasing 

 in favour, so that now a piece of rock- work devoted to these inhabitants 

 of the hills is almost a necessity in any garden where an attempt is made 

 to minister to the needs of the various classes of plants deemed worthy of 

 cultivation. While the majority of alpines are of the easiest culture, 

 many of them need special treatment, and some few others are the despair 

 of the gardener : no soil or situation seems to please them, and all the wile3 

 of the most experienced grower are lavished on them in vain. I have 

 spoken of alpines and rock plants, and it may be asked why these two 

 classes of plants are grouped together. It might be said that the conditions 

 under which they grow are widely different ; that the flowers which brave 

 the frost and snow and storms of the elevated regions would differ al- 

 together in their requirements from those which nourish on dry hot rocks 

 in the plains. And this brings us at once to the question as to what are 

 the special features of alpines and rock-plants, and why we award them 

 special treatment in the garden. 



If we examine a series of plants whose home is on dry rocks or high 

 mountains, a general similarity of form will be observed, and several 

 peculiar features common to both groups will force themselves on our 

 attention ; — their dwarf stature ; their tendency to form close cushiony 

 masses ; the frequency with which they display a dense covering of hair 

 or felt, or a tendency to succulence ; and the size and brilliancy of their 

 short-stemmed flowers. And all these features are explained when we 

 consider the conditions under which they live. Whether on lowland 

 rocks or highland slopes, these plants suffer great exposure to wind, and 

 tall or loose or straggling forms would be broken ; but dwarf bushy 

 growths successfully weather the worst storm. Exposure to burning sun, 

 also, is excellently met by a cushiony growth, with the roots well tucked 

 in under a dense mass of stems and leaves. Again, in alpine regions the 

 summer is very short. After the snow has passed away, there is no time 

 for the formation of tall or elaborate stems. Within the space of perhaps 

 three months, the whole cycle of growth — leaf, stem, flower, and fruit — 

 must be performed ; and hence our characteristic alpines are close-growing 

 things, with flowers nestling close down to the leaves. Next, guarding 

 against drought is a very important matter for all plants which grow in 

 dry places. Dry winds — whether the scorching winds that blow across 

 Arizona deserts or the icy breezes of alpine regions— are especially dangerous 

 to the proper fulfilment of the functions of leaves and stems, causing as 

 they do an excessive loss of water from the surface of these organs. We 

 find in alpines and rock-plants various devices for hindering undue loss 

 of water. The general reduction of the surface, effected by the close 



