74 PLANTING 



1. The Demands of Trees as to Moisture. 



The amount of moisture, both in the soil and in the 

 atmosphere, is perhaps the most important consideration 

 affecting tree growth. The majority of trees prefer a moist 

 atmosphere ; especially is this the case with Sitka Spruce, 

 Sitka Cypress, Norway Spruce, Silver Fir, Douglas Fir, 

 Thuya gigantea, Ash (European), most Poplars, Alder, Cup- 

 ressus macrocarpa^ and Spanish Chestnut. 1 However, Scots 

 Pine, Austrian Pine, and Corsican Pine prefer a dry atmo- 

 sphere. 



Then again, the majority of trees require a plentiful 

 supply of moisture in the soil for their healthy development 

 and to make good the losses caused by transpiration. This 

 is especially the case with the above class requiring a moist 

 atmosphere, and so also with Tree Willows, White Poplar, 

 Black Poplar, Black Italian Poplar (P. Canadensis), Peduncu- 

 late Oak, Hornbeam, and Weymouth Pine. 



Trees such as Sycamore, Norway Maple, Beech, 2 Sessile 

 Oak, Larch, and Elm will succeed with rather less moisture. 



The White Ash (F. Americana) will thrive on soils far too 

 dry for the Common Ash. So too, White Alder and Abies 

 concolor. Aspen Poplars, and Walnut trees will grow on 

 quite dry soils, and (perhaps) Sitka Cypress. 



The best trees for very dry soils are Scots Pine, Austrian 

 and Corsican Pines, Acacia, Birch, and Mountain Ash. 



Those trees thriving on dry soils, will, generally speaking, 

 thrive also on soils containing more moisture. 



Birch is the most accommodating tree of all, and will grow 

 practically anywhere, even on sour, ill-drained soils. But, 

 with the exception of Birch, no trees can grow on ill-drained 

 land which is sour, or wet with stagnant water. 



A moderate excess of water, provided it be well aerated 

 and is not stagnant, is not detrimental to Alder, Willows, 



Spanish Chestnut will grow in a dry atmosphere and on fairly dry 



soil, but the timber is then usually very shaky ; whereas, with sufficient 



moisture, and other conditions suitable, it is usually of very fine quality. 



2 Beech will thrive with considerably less moisture, on chalk and 



other limestone soils, than otherwise appears necessary for its well-being. 



