A HANDBOOK FOR EUCALYPTUS PLANTERS. 



33 



The blue gum has gained the reputation of possessing a phenomenal 

 rate of growth, and by an inspection of the figures of average and 

 maximum growth this may be appreciated. Under favorable conditions 

 trees in seedling plantations have reached a maximum development of 

 5 inches in diameter and 67 feet in height in four years. This represents 

 an average of 17 feet height growth per year, though a growth of 10 to 

 15 feet in height yearly is the general average. In the height of the first 

 growing season seedlings have frequently been observed to make an 

 average height growth of 6 inches a day. The most rapid seedling 

 growth noted was made by a tree which in nine years reached a height 

 of 125 feet and a diameter of 36 inches. As is usual among vigorously 

 sprouting trees, sprouts upon old root systems surpass seedlings in rate 

 of growth. Ages are occasionally recorded in the sprout tables in frac- 

 tions of a year, representing the number of months' growth. In eight 

 months a maximum diameter of 3 inches and 34 feet height has been 

 reached while in three years a maximum diameter of 7 inches and 70 

 feet in height has been attained. 



In different groves and even upon different sample plots in the same 

 grove a considerable variation in yield is shown, often ranging from 

 maximum to minimum upon the same soil. This variation is determined 

 to some extent by the character of the planting site, the permeability of 

 the soil and the moisture available, and partly by the density of plant- 

 ing. It is governed mainly, however, by the density of the present stand 

 of trees in consequence of the treatment accorded after planting. The . 

 deterioration of a grove because of lack of cultivation or protection, or 

 from neglect after cutting, is sufficient to reduce the yield to a mini- 

 mum on sites capable of maximum production. Unfortunately, the 

 variation of this factor prevents its use in the construction of tables. 



Sufficient data are not available from the measurements of young 

 plantations to construct a complete table, giving the yield of poles and 

 piles at different ages. A tree with a butt diameter of 9 inches is 

 required to produce a pole of the smallest merchantable size, namely, 

 20 feet long with a top diameter of 7 inches. Sprout stands are usually 

 cut before eight years of age, and, in this time the yield of poles is low, 

 since few trees in dense sprout stands attain the butt diameter required. 

 The acre yield of poles having a top diameter of 7 inches from two 

 representative seedling plantations of maximum growth has been esti- 

 mated as follows: 



TABLE 11. Yield of Poles per Acre. 



Each of these acres yielded, in addition, 30 cords of fuelwood. 

 3 BF. 



