THE LAYING-OUT OF A MIXED PLANTATION. 51 
As most of our forest trees are liable to accidents and diseases, 
it is necessary, when thinning, to remove those of poor growth, 
or showing signs of premature decay. Those left should be the 
largest and most promising trees, and though they may not 
stand at regular distances apart, this can be rectified during 
successive thinnings. When trees have stood long enough in 
close canopy to be drawn up tall, clean, and straight, it will 
then be advantageous to thin gradually, before they become too 
tall and slender in proportion to their girth. 
The intervals at which thinnings should take place depends 
on the kinds of trees, closeness of planting, soil, and situation. 
Trees differ in their requirements for growing-space, and other 
factors also exert their own special influence. Care should be 
taken not to interrupt close canopy unnecessarily by removing 
too many trees at one time, and thus unduly exposing the soil 
to the effects of wind and sun. 
In timber-crops grown for profit, the thinnings should be made 
so as to benefit the most promising trees, because excessive 
thinning at this stage often means future loss on the mature crop. 
When our timber is by chance or good management grown in 
close canopy, it is equal in quality to imported timber, and can 
be applied to much wider uses than at present. 
The first thinning of hardwoods mixed with conifers is a 
simple operation, consisting principally in the removal of some 
of the conifers. As fast-grown hardwoods are much more profit- 
able than slow-grown, their growth should be encouraged by 
Opening out the crop as soon as, and so far as, this can be done, 
while still keeping the formation of unnecessary side-branches 
in check; but, of course, healthy conifers should be retained 
where the hardwoods show signs of failing health. 
The margins of plantations require different treatment as to 
thinning, as the trees are here intended to form a barrier to the 
wind, and give shelter. It will therefore be necessary to thin 
before the trees get crowded and lose their side-branches, because 
these should be preserved and encouraged from the very earliest 
stages, so as to provide shelter to the interior of the plantation. 
When margins are formed of hardy trees, clothed to the ground 
with healthy, well-balanced branches, they resist violent gales, 
and prevent the wind from sweeping underneath, carrying away 
the dead leaves, and depriving the crop of nourishment. 
