willows: their growth, use, and importance. 11 
The bark of the forest-grown black willow varies considerably. On 
trees 2 feet or more in diameter it is usually 1.2 to 1.5 inches thick at 
stump height, as measured by the caliper or diameter tape. Typi- 
cally it is rather soft and easily broken and sometimes hangs in loose 
flat scales. Occasionally it is very hard, the ridges being, therefore, 
deep. 
The black willow has no pronounced taproot, although there may 
be several smaller roots extending downward beneath the trunk of 
the tree. On well-drained soils it develops a lateral root system, and 
on poorly drained soils where the water table is habitually near the 
surface of the ground the root system is decidedly lateral, uprooted 
trees often showing a depth of root of less than a foot. 
TYPES AND ASSOCIATED SPECIES. 
Practically all black willow stands have originated along the low 
banks of streams or lakes or have gained a foothold on areas which 
have received a generous deposit of sediment. The pure stands are 
usually on the lowest land or first bottoms. On the higher ground 
the willows are found to be mixed more and more with other species ; 
in the North, principally elm, maple, ash, cottonwood, and boxelder, 
and in the South, cottonwood, with small amounts of ash, maple, 
sycamore, or cypress. The southern black willow stands must be 
considered temporary. Most of the land on which they are found 
is accretion land. Along the Mississippi the willow lands extend 
ordinarily from the water level to 35 feet, above it, although the 
drainage conditions are more important in deciding this than the 
actual height of the land. In the extreme South, where there is a 
much larger area of bottom land than in the North, poor drainage 
results in the appearance of such species as cypress, water oak, and 
red gum in places where, with better drainage, cottonwood and 
willow would have been the first stand. The willow stand, whether 
it be along the rivers or in prairie plantations, must always be con- 
sidered an advance guard or pioneer stand. As soon as soil or 
economic conditions improve it is generally replaced by other species. 
GROWTH OF BLACK WILLOW. 
HEIGHT GROWTH. 
Black willow grows very rapidly in height, not only because of its 
inherent vigor but also as a result of the intense competition for light 
which is caused by its intolerance and the density of the stands in 
which it naturally comes up. Both the annual growth and the total 
height attained by the mature tree are greater in the South than in 
the North. Table 1 shows the average height of stands of approx- 
imately the same age at different points in the Mississippi Valley. 
