44 BULLETIN 13, U. S. DEPARTMENT OF AGRICULTURE. 
couraged, provided the pines have received a sufficient start to keep 
their crowns above those of their associates. The diameter growth of 
pine in suitable mixtures, unlike that in pure stands managed on 
short rotations and unpruned, is accompanied by a marked improve- 
ment in the quality of the lumber, due to its greater freedom from 
knots. This comes about through the natural pruning of the pine 
branches by the relatively low and supple hardwood crowns. An- 
other advantage of mixed stands consists in the relative freedom of 
the pine tops from damage by weevils, due to the isolated position 
of the pine among broadleaf trees inhabited by insect-eating birds. 
Among the trees desirable for cultivation with white pine are 
beech, sugar, and red maple, yellow birch, basswood, red oak ? 
white ash, and black cherry. These are arranged approximately 
according to ability to endure shade, beech being the most 
tolerant, cherry the least. Though their present economic value 
is relatively low, the tolerant species except red maple are also 
the slowest growing, which enhances their value as an understory 
for white pine. Cherry, ash, and red oak, on the other hand, pro- 
duce lumber fully as valuable as that of white pine, but their rate 
of growth is only a little slower than that of the latter. Each class of 
associates, therefore, has a characteristic value in mixture with pine. 
As compared with pure stands managed on short rotations, the 
yield of the latter in a mixed stand may be considerably reduced, 
but where a higher quality of pine lumber is desirable and a market 
exists for the hardwoods, mixed stands operated on somewhat longer 
rotations are worthy of consideration. 
Among the inferior associates of white pine are gray birch, large 
and small toothed aspen (popple), fire cherry, pitch pine, and jack 
pine. Most of these are undesirable simply because they monopolize 
ground upon which better species might be growing. Gray birch, 
however, is an active menace to any young pine in its vicinity, since 
its sprouts, swaying in the wind, soon kill the tender upper shoots of 
young pines growing near them. 
TREATMENT. 
The success of pine among hardwoods depends, for one thing, upon 
its overtopping the other species. This can usually be brought about 
by one or more disengagement cuttings made at about the time the 
pine is entering upon the period of its most rapid height growth. To 
secure mixed stands, of course, disengagement cuttings need not be as 
thorough as for pure pine stands, since the pines will be scattered, 
and only the hardwood saplings near them need be cut. It will be 
well, however, to remove inferior trees like gray birch, aspen, and fire 
cherry wherever they appear to threaten the existence of better 
species, such as white ash, red oak, and black cherry. Subsequent 
