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SECTION V. 
HARVESTING OF THE TIMBER CROP. 
SIZE AND MATURITY OF EUCALYPTUS TREES 
IN ECONOMIC FORESTRY. 
1 he heights and girths of Eucalyptus trees mentioned in books and catalogues 
usually refer to indigenous specimens favourably situated and probably centuries 
old. The statements, so far as they are correct, are very interesting from a purely 
scientific point of view; but to the practical tree planter they are of little value and 
may be misleading. The man who is planting for utility cannot always choose for 
his purpose deep sheltered valleys, nor can he anticipate the growth of centuries. 
He is looking for profit in his own lifetime, or at most within that of his children. 
He probably has to face average conditions of soil and situation, and he wishes to 
know what size his trees may be expected to reach in those conditions within twenty 
to thirty or forty years. 
For economic purposes very big trees are really not desirable. If a tree is 
excessively tall and slender in stem diameter, it is liable to break in falling. If the 
diameter is very large, the logs will be too heavy for handling and beyond the 
capacity of any ordinary saw. A larger number per acre of smaller trees will 
usually, therefore, be a more profitable crop than a smaller number of very large 
ones. Diameters of stem measuring two to three feet and total heights of one 
hundred to one hundred and fifty feet will be found about the maximum for 
convenient conversion to use. With the most rapid-growing species favourably 
situated these dimensions may be reached within thirty to fifty years. For many 
purposes, if the tree is mature, a less diameter will be ample. 
On the question of maturity there is no fixed standard; but it may be said in 
a general way that a Eucalyptus tree is mature when 75 to 80 per cent, of its bole 
has changed into mature wood. When a tree has matured and reached its best it 
should be felled and utilized. To keep it standing longer means only loss. There 
will be loss not only of interest on the timber value of the tree, hut probably also 
deterioration of the tree itself. In all living nature maturity is sooner or later 
followed by decay. Mature wood (heartAVOod or duramen), as we have seen, has, 
like the external sapless bark, ceased to be a living part of the tree. It may 
persist for a long period in an almost unchanged condition, or it may soon 
deteriorate, the time and rate of decay being determined by the genus and species 
to which the tree belongs and by the soil upon which it is growing. New Zealand 
bushmen are familiar with what is called honeycomb in the centre of very old 
totara trees; and timber men generally are well aware that some form of heart 
deterioration is one of the things against which they have to be on their guard in 
purchasing any over mature trees. The central heartwood of over mature 
Eucalyptus trees first becomes brittle, then soft, and ultimately powdery. This is 
not identical with the decay that takes place when the timber is exposed to the 
w 
