8o TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



it would greatly extend the area of land economically afforest- 

 able. The same applies to water supply. Moist soil and 

 humid atmosphere undoubtedly increase the growth of this 

 species, but we should attempt to determine its minimum 

 requirements as regards these factors. Swampy conditions are 

 unfavourable. It is fairly certain that a considerable degree 

 of shelter is necessary, especially from drying winds, otherwise 

 the branches turn red and die. Douglas fir grows up to 

 5000-7000 feet above sea-level in the Rocky Mountains, and 

 there appears to be no reason why we cannot grow it up to 

 elevations of 1500 feet provided ample shelter is available. 

 It is already giving good results in this country at elevations 

 of 1000 feet above sea-level. In its early life it is liable to 

 damage from late and early frosts, but any available nurse, such 

 as birch, will greatly lessen such damage. 



Until its requirements are fully investigated, this species 

 should only be planted on fairly fertile, deep, moist soils, with 

 ample shelter and with an aspect other than S.E., in order to 

 mitigate against frost damage. 



Under favourable conditions this species gives remarkable 

 results as regards height-growth and production. At 50 years 

 a height of 80-100 feet and a volume-production of 5000- 

 7000 cubic feet can be expected. The Blue Douglas is much 

 less productive, but, nevertheless, it may compare favourably 

 with other species under the less favourable conditions. 



The timber of Douglas fir is very variable in density, quality, 

 and thickness of sapwood even in its habitat. At its best it 

 approximates to larch but is lighter. In America the timber 

 is used for all kinds of construction, sleepers, etc. The timber 

 of this species grown in this country requires careful testing 

 both mechanically and in use under different conditions. 



The earlier woods of this species planted in this country were 

 in most cases a mixture with larch, as at Taymount in Perthshire 

 and Llandinam in Wales, or with spruce, as at Gairloch in west 

 Ross-shire. The larch was rapidly killed by the Douglas so 

 that the latter species grew up under fairly open conditions. 

 Even when planted pure as at Tortworth, Glos, the planting 

 distance was wide, namely 12-15 ^ eet - Later, the other 

 extreme was reached. It was planted pure and dense, in some 

 cases 3 feet apart. Douglas fir is a rapid grower throughout 

 life, but especially in early life. When planted 3-4 feet apart 



