FOREST PLANTING IN THE EASTERN UNITED STATES. 17 
Another objection to pruning is the danger of overdoing it. If a 
tree is pruned too far up it may become top heavy and be broken off 
in a severe wind. Catalpa, ash, and black cherry are particularly 
susceptible to injury in this way. The stems of young black cherry 
and ash, when pruned far up, bend over by their own weight nearly 
at right angles. Sucker sprouts then shoot up from the bent stems, 
making.a deformed tree. In a stand of black cherry 8 years old in 
Indiana, where the trees were pruned to a whip, 11 per cent had been 
broken off by the wind. 
Pruning also reduces the amount of leaf surface, the food-making 
part of the tree, and hence reduces its rate of growth. 
Hspecially valuable species and trees with very persistent branches 
should be trimmed at least of their dead branches and sometimes of 
their livmg ones. Of the species commonly planted, white pine, 
black walnut, hardy catalpa, and black locust sometimes need 
pruning. 
The lower branches of white pine are large and persist for many 
years after dying. Sometimes, but not as a rule, it will be profitable 
to prune the best trees m the stand by simply knocking off the limbs 
with an axe after they are dead and have become brittle. Black 
walnut seldom needs pruning, though occasionally dead branches 
persist for a number of years which are likely to form loose knots 
in the lumber. Such branches should be removed. Hardy cataipa 
has very persistent branches, though the presence of knots in fence 
posts, the chief product of catalpa plantations, scarcely impairs 
their value. The dead branches are objectionabie, however, because 
they become loose and allow the entrance of wood-rotting fungi. 
Since, therefore, these branches are a menace, they should be removed. 
Catalpa, moreover, does not form a terminal bud, but ordinarily 
develops three buds at each node. From those at the node nearest 
the tip of the last year’s shoot three new shoots arise, any one of 
which may develop into a leader. In order to increase the devel- 
opment of one of these shoots and thus control the tree’s form, one 
or both of the other two shoots on the node should be removed. 
An effective and cheap way of doing this is to pinch off these shoots 
just as they are developing from the buds. Black locust ordinarily 
prunes itself readily, but when widely spaced the main stem often 
forks into two or more main branches. In one young plantation 
of black locust in Illinois, spaced 8 by 11 feet, fully 43 per cent of the 
trees showed this fault. Such trees should if possible be pruned of 
all but one of their leaders. 
The lower branches of Norway spruce are very persistent, but 
not very large; hence for ordinary purposes the tree requires no 
pruning. The ashes ordinarily prune themselves of their lower 
60370°—Bull. 153—15——3 
