TREES FOR WATER CATCHMENT AREAS 145 
second year, they can be planted out when three or four 
years old (Fig. 22). Tsuga Albertiana 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 
North 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, 
L 
