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 



