TEEES FOE WATEE CATCHMENT AEEAS 145 



second year, they can be planted out when three or four 

 years old (Fig. 22). Tsuga Alhertiana grows well on 

 most soils, except on chalk and stiff clay. It is at home in 

 a mild climate, and will not bear great exposure. It suffers, 

 however, less from wind than Douglas fir. There is little 

 inducement to attempt its cultivation as a main-crop tree ; 

 but it may be planted as a soil -improving species in 

 company with larch ; and it can be used to fill up blank 

 spots in open woods, as it bears a considerable amount of 

 lateral shade. 



Thuya gigantea. — This species is widely spread in western 

 Nortli America, where it is usually found growing isolated 

 or in small groups amidst other species, mostly in moist 

 valleys and along water courses, and attaining its largest 

 size in Vancouver Island and the adjacent coast of the 

 mainland in a humid climate. It is very vigorous in growth, 

 but inferior in this respect to Douglas fir and Sitka spruce. 

 It is an intense shade-bearer, rapidly covering the ground ; 

 and cleans its stem with the greatest difficulty, the branches 

 persisting till late in the life of the tree. The wood is light, 

 strong, and very durable. 



Thuya gigantea has been much recommended for planting 

 in this country, and has considerable merits. It is for so 

 far a very healthy tree, free from insect and fungus attacks. 

 It may be cheaply raised from home-grown seed, and can be 

 planted out with the greatest ease. It is most suitable for 

 damp and peaty soils in humid climates ; and has succeeded 

 remarkably well on the Benmore estate, Argyllshire, where 

 it is mainly grown (Fig. 30) in mixture with Douglas fir, 

 and regenerates itself freely from self-sown seed. It grows 

 also fairly well on shallow oolite and chalky soils. It can 

 be planted pure, or in mixture with Douglas fir, larch, or 

 Sitka spruce. The main objection to extensive use of the 

 Thuya is that clean timber cannot be expected from it, 

 unless it is grown on a very long rotation. It will ordin- 

 arily produce knotty poles, which are, however, very durable 

 and useful for many purposes, as for pitwood, fencing, 



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