THE ASHES : THEIR CHARACTERISTICS AND MANAGEMENT. 39 
ROTATION. 
Ash should be grown, as a rule, on comparatively short rotations 
of 30 to 60 years. Table 18 shows that the best financial rotation, 
or one which will yield the highest rate of interest on the money 
invested, falls between these years. The financial rotation is length- 
ened by low yields, low stumpage values, and high initial investment, 
while the opposites of these shorten it. The actual rotation in any 
particular case may be altered from what seems to be the best finan- 
cial rotation by a number of factors, including the purpose for which 
the timber is grown, the condition of the market, and the occurrence 
of seed years. 
From a silvicultural standpoint a short rotation is highly advisable 
for pure even-aged stands of ash, because of the tree's root and 
crown requirements. Long rotations in pure stands should be prac- 
ticed only on the best sites, and in some cases where a long rotation 
is desired the stand should be heavily thinned out and under-planted 
after it is 40 to 50 years old, to protect the soil. In mixed stands 
where it is the favored dominant tree ash can often be grown singly 
or in small groups on a long rotation. 
SPECIES FOR COMMERCIAL TIMBER GROWING. 
Species of the white and green ash groups are more desirable for 
commercial timber growing than those of the black ash group, because 
their wood is superior in mechanical properties and because they are 
usually faster growing and attain greater length and clearness of bole. 
There are two classes of sites, however, where for silvicultural reasons 
it may be advisable to grow ash of the black ash group — namely, blue 
ash on dry limestone formations of the Central States and black ash 
in northern swamps. 
There is no great variation in the mechanical properties of the 
different species of the green and white ash groups, and little or none 
in the sale value of lumber of the same grade from different species, 
so that the selection of species for commercial growing from these 
groups depends entirely on their silvicultural qualities. In general, 
the species which is most common to the region and character of site 
in question should be used. The growing of species outside their 
natural habitat (of region and site) should never be tried on more 
than an experimental scale. White ash will be the species to use, 
as a rule, in the New England, Middle, Central, and Lake States and 
in the hills and mountains of the South; and green ash on river 
bottom land of the Southern, Central, and Plains States. Of very 
minor importance will be the growing of Oregon ash on the Pacific 
coast and of leather-leaf ash (F. velutina) in the Southwest (the latter 
for shade, ornament, and protection). Biltmore ash is an important 
