90 PLANTING 



.} And as regards the conditions under which they may 

 best be grown, it is necessary to consider : 



(1) The Age and Distance apart at which trees should 



be planted. 



(2) The Merits and Demerits of Pure and of Mixed 



Woods, and the Methods of mixing. 



(3) The Choice of System under which the crops may 



preferably be grown. 



(4) The advisability, or otherwise, of a rotation in 



cropping. 



(5) The Season for Planting. 



(A) CONCERNING THE GROWTH PECULIAR TO 

 INDIVIDUAL TREES. 



(1) The Shape of the Crowns. 



This is a matter to which due consideration must be 

 given when planting mixtures of trees, or when contemplat- 

 ing underplanting, etc. For the final development of the 

 crowns will, to a great extent, determine the ultimate number 

 of trees that may be left per acre for the final crop, and the 

 individual growing space they require. All the broad-leaved 

 trees and Scots, Corsican, and Austrian Pines naturally 

 develop a wide branching crown as they grow old. Whereas 

 Douglas Fir, Larch, Silver Fir, Spruce, and Weymouth Pine, 

 never normally develop a large crown, but preserve their con- 

 spicuous central axis even in old age ; though, if grown in 

 the open, they will generally be clothed to the ground with 

 a luxuriant growth of side branches. The Sessile Oak grows 

 naturally with a much straighter stem than the Pedunculate 

 Oak ; and it is less inclined to form a spreading crown. 



As regards those trees which naturally form large crowns, 

 it may be mentioned that crown development should be 

 suppressed until the principal height growth is attained, but 

 that, after that period, it must be encouraged to a very con- 

 siderable extent, or the trees will unduly suffer. 



