370 SYLVICULTdRAL NOTES ON TIMBER TREES 



But it will also grow on the very stiffest of clay soils ; 

 and, on such soils, it is probably the most profitable tree to 

 plant. 



The tree appears quite immune to spring and autumn 

 frosts, and hence is of the utmost value in many cases. 



Cultivation, etc., is similar to that described for the 

 Black Poplars. 



The tree throws out innumerable root suckers, and spreads 

 naturally by such means. 



Rotation. This should be from 50 to 60 years. 



THE GREY POPLAR. 



This is not a native tree. 



It is probably an hybrid between P. alba and P. tremula. 



It is very similar in all respects to the White Poplar ; and 

 thrives under the same conditions. 



It is raised from suckers, which are developed in great 

 profusion. 



It will grow in rather drier localities than the Black 

 Poplars or the White Poplar ; and like the White Poplar, it is 

 very frost-hardy. 



THE ASPEN POPLAR. 



This is a native tree to this country. 



As to Seed. The seed ripens about the end of May, and, 

 like all Poplar seed, must be sown at once. 



It is generally raised from root suckers, and sometimes 

 by layering. Cuttings are not very successful. 



The timber is white and brittle, and is inferior to that of 

 the White Poplar, being worth from J to f as much. 



Soil and Situation. It will grow on any soils suited to 

 the other Poplars just described. But it will also grow on 

 drier soils than the other Poplars will grow upon ; and also 

 on more shallow soils. It can exist on very dry soils, but its 

 growth is then poor. 



It is very frost-hardy. 



Cultivation, etc. The Aspen must usually be regarded 

 as a weed. It may be used in the place of Birch, as a pro- 



