22 The Amateur's Book of the Dahlia 



slope of the Sierra de Ajusco, south of the Valley 

 of Mexico, is known locally as the Pedigral or 

 Stony Place, where lava beds of centuries ago 

 still hold the fantastic forms they took when 

 these mountains were venting their fury. There 

 the dahlias flourish in all their glory acres and 

 acres of them in every hue and colour. 



Three of the eight varieties of dahlias known 

 to grow in Mexico are to be found here. Of the 

 others, some grow in even higher altitudes, 

 and some in other localities. Of these, Dahlia 

 coccinea is the hardiest, and was probably what 

 Cavanilles first had in his garden in Madrid. 



This Pedigral is not the only place where wild 

 dahlias grow in such profusion. There are many 

 such spots on the volcanic mountain slopes 

 where their roots may delve among the crum- 

 bling lava which feeds them and keeps them cool 

 and moist. Low-hanging clouds, swinging among 

 the hills, temper the sun and bathe them with the 

 dew so necessary for their existence. 



All during the late summer and early autumn 

 these dahlias keep up their mass of bloom; but 

 in October and November, when the daily show- 

 ers cease and the "dry season" sets in in earnest, 

 the moisture stored up in the "water-pipe" 

 stem gradually goes back to the mother-tuber 

 and nourishes it until it is time to sprout again. 



