THE ENEMIES OF ENGLISH WOODLANDS 313 



extent, and, as such trees are rarely of much value for timber, 

 their value standing is greater than when down. 



Careful thinning, good drainage, and a certain proportion of 

 naturally deep-rooting trees in the crop itself, are all favour- 

 able to the avoidance of damage in ordinary plantations. 

 Careful thinning prevents the swaying of the crowns, which 

 is the cause of immediate injury. Good drainage encourages 

 a deep and well-developed root system, while deep-rooting 

 trees give the plantation a stiffness and rigidity it would not 

 otherwise possess, when the crop chiefly consists of shallow- 

 rooting conifers. In spite of all precautions, however, some 

 damage must be expected from severe gales, and it is a well- 

 known fact that there is no certain relation between this 

 damage and the sheltered or exposed condition of the 

 situation. 



Late Fkosts. 



Late frosts are clearly beyond the power of the forester 

 to control or prevent, and it is only possible to minimise 

 their effects by planting hardy species in situations most 

 exposed to them. Such situations are damp hollows, or flat, 

 low-lying land which is favourable to stagnant air during 

 windless nights. Where ground to be planted occupies a 

 large area of flat land, it may not always be possible to 

 select none but hardy species. In such cases any tender 

 species must be protected by older and larger trees during 

 the early stages, so that the critical stage of its existence, 

 which may be said to be that period during which the 

 leading shoots are within 20 feet of the ground, may be 

 safely gone through. Ash, beech, Douglas fir, silver fir, 

 etc., are all particularly sensitive to late frosts, and, when 

 planted on ground subject to them, a hardy species, such as 

 birch, elm, Scots fir, etc., should be planted in advance, and 

 allowed to reach a height of 20 to 30 feet before the others 

 are introduced in the form of a second storey. 



In frosty hollows of small extent tender species should 

 never be planted, and only those able to endure a spring 

 frost in April or May of three or four degrees are fit for 

 such spots. 



