46 FOREST CULTURE AND 
an age of fifty years, and yet is not prevented by this 
crowded growth to be then one hundred feet high ; 
the stems are then very straight, eighteen inches in 
diameter at the base. If Pines and Oaks are promis- 
cuously planted, then the former, which act as nurse- 
trees, are moved in ten or twenty years, and the 
ground is left to the Oak, or any other deciduous 
tree, at distances at first ten or twelve feet apart, and 
subsequently wider still, No decayed wood is left 
in planted forests, as it would harbor boring insects. 
Pines are considered not to increase much in value 
after eighty years, when most of them have attain- 
ed full maturity, and grow only afterward slowly. 
Sometimes as many as one thousand two hundred 
Pine-trees are set out on an acre, with a view of early 
utilization of a portion of the young trees. The rate 
of growth may be much accelerated in most trees 
by irrigation ; hence mountain streamlets should be 
diverted into horizontal ditches where forests are 
occupying hill-sides. The best-cultivated forests of 
Germany are worth from three to five times as much 
as native woods. 
For shelter plantations, intended to yield ultimate- 
ly also timber and fuel to farming populations, it is 
recommendable to adopt the American method, ac- 
cording to which belts of trees are regularly planted 
at about quarter-mile distance; the belts, according 
to circumstances, to be from four to ten rods wide, 
and to be formed in such direction as to front the pre- 
vailing winds. These timber-belts are usually fenc- 
ed. Such shelter-trees are likely to rise to thirty 
feet in ten years, and have proved so advantageous 
as to double the farm crop, while judicious manage- 
