best on deep, loose sandy loams, because these soils commonly 

 occupy bottomlands which are fully supplied with soil moisture. 

 In shallow soils overlying rock or hardpan, where the roots are 

 forced to spread widely near the surface, the growth of the tree is 

 usually stunted. 



Blue gum grows well in situations where the ground water level 

 is very close to the surface, and it will even endure standing water 

 for short periods. It grows very rapidly under irrigation. As a 

 rule, however, irrigated land is too valuable to be used for commercial 

 plantations and usually it may be more profitably devoted to agri- 

 cultural crops. Irrigation is not necessary for old, deep-rooted trees. 



In situations along the coast where rainfall and soil moisture are 

 deficient, fogs furnish an important source of moisture supply for 

 eucalypts. Fogs frequently enable blue gum to make thrifty growth 

 on dry upland situations in other respects very unfavorable for it. 



Blue gum is relatively intolerant. Young seedlings thrive under 

 considerable density of shade, but when rapid growth begins seedlings 

 are unfavorably affected by shading. The intolerance of saplings 

 and poles is in a measure indicated by rapid height growth, upon 

 which they depend to escape suppression, and is further shown by 

 the fact that even in the open the lower branches are shaded out 

 by the upper branches, so that the trunks rapidly clean themselves. 

 This species may be grown in very dense plantations where all trees 

 obtain an equal start. 



Compared with most native trees, blue gum has a phenomenally 

 rapid rate of growth. Seedling stands will average a height growth 

 of 50 feet in six years and 100 feet in ten years. Under very favor- 

 able conditions individual trees have reached a height of 125 feet and 

 a diameter of 36 inches in nine years. In sprout stands growth is 

 even more rapid; trees frequently reach 3 inches in diameter and 35 

 feet in height in eight months, while in three years a diameter of 7 

 inches and a height of 70 feet are often attained. 



Blue gum is practically immune from disease. Where trees are 

 reproduced by sprouts, the old stumps frequently decay slowly at 

 the heart, while the sprouts remain unaffected. Growing trees are 

 not attacked by insect enemies, but felled timber lying unbarked 

 upon the ground is subject to injury by a wood-mining insect. 



Blue gum rarely suffers any breakage of the limbs from winds, 

 and the spreading root system renders the trees very wind-firm. 

 However, severe and constant winds have a very injurious influence 

 upon the growth of all eucalypts. Inland winds cause little dam- 

 age. Along the coast, however, exposed trees show the effect of the 

 strong western winds in distorted form and stunted growth; they 

 gradually become defoliated and are sometimes killed. 



[Cir. 59] 



