PRUNING OF FOREST TREES. 69 
shoots spring from the cuts, and these are again cut when of 
suitable size. What has been said in regard to the season and 
manner of cutting in the previous paragraphs is practically true 
here. This process is mostly used in the case of willows and 
poplars to obtain material for basket work, small poles, fuel, etc. 
Time of Rotation is a term used to indicate the age to 
which trees are grown. The length of this time will depend on 
the species and on the conditions. For some species not less 
than eighty years should be allowed for full maturity, while still 
others may be successfully worked on a thirty-year rotation 
period. It is not used in the same sense as in ordinary agri- 
cultural operations, where it signifies frequent changes of the 
crop for several years with a view to getting the most out of the 
soil. Since trees do not impoverish the soil, but improve it, 
there is no necessity for any such method of rotation in forestry 
as there is in agriculture. 
Pruning of Forest Trees is generally an expensive opera- 
tion and little is required if trees are properly crowded when 
young, so that they take on an upright form free from side 
branches. If they are not crowded when young, many side 
branches are formed, which generally die out when the trees get 
large enough to shade all the ground. In some cases these dead 
branches drop quickly to the ground, and in others they remain 
for years, producing knots and irregularity in the wood formed 
in the meantime and should be removed. Trees grown in the 
open retain their lower branches more or less throughout life 
and they produce in consequence timber of inferior value as 
compared with trees grown in crowded woods. 
Large wounds made by cutting off green branches should be 
covered. It is often desirable to remove dead branches and it 
is the practice to do so in some of the plantings of Wnite Pine 
that have been made in New England. It is said that the lum- 
ber there is so greatly improved by so doing that the operation 
is a paying one. But under ideal conditions for the develop- 
ment of timber trees very little is gained by pruning. 
The Young Growth is Often Injured in ordinary lumber- 
ing operations by the felling of the trees, which bend them to the 
ground and often break them. Where special care is desired to 
protect the young growth it may be desirable to lop off the 
