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BLUE GUM (Eucalyptus globulus). 

 FORM AND SIZE. 



Blue gum is an evergreen tree, with smooth, elongated, sickle- 

 shaped leaves, dark green on both sides, and of leathery texture. 

 The young leaves are of a globular shape and are covered with an 

 oily bloom which gives them a bluish shade. The bark of the tree is 

 smooth, and olive brown in color. The large, rounded, top-shaped 

 seed-cases, covered with warty protuberances, furnish the most dis- 

 tinguishing characteristic of the tree. 



Blue gum is one of the largest and most rapid growing trees in the 

 world. In California, under favorable conditions, trees have attained 

 a height of 175 feet and a diameter of 5 feet in twenty-five years. 

 Although sometimes irregular in form, the tree tends to develop a 

 straight, gradually tapering, unforked stem. In plantations the 

 trunks become rapidly cleared of branches to a considerable height, 

 but in the open, trees branch more widely, and gradually develop a 

 short crown of massive, spreading branches. 



RANGE. 



Its intolerance of frost restricts the planting range of blue gUm 

 in this country almost entirely to the temperate valleys of California. 

 Young blue gums are especially sensitive to frost, and will seldom 

 endure a temperature below 24 F. Old trees are more hardy, and 

 generally are uninjured by a temperature as low as 18. 



The planting range of blue gum in California includes the greater 

 part of the agricultural area of the State. The tree resists drought 

 to a moderate extent only, and becomes stunted when planted on 

 dry uplands or in the hot interior valleys. It reaches its best 

 development in the humid coast region and in the valleys which 

 open from it. 



HABITS AND GROWTH. 



The most essential requirement of blue gum and other eucalypts 

 is an adequate supply of soil moisture. A warm climate, a dry 

 atmosphere, and a high percentage of sunlight furnish very favorable 

 conditions, and when abundant moisture is found within from 10 to 

 15 feet of the surface blue gum will grow well even in dry situations. 

 In the more arid interior valleys of California, however, where tem- 

 peratures of from 110 to 140 F. occur, together with great atmos- 

 pheric dryness or with hot, dry winds, the foliage of the tree is likely 

 to be burned and injured. 



Blue gum develops an extensive root system which penetrates 

 deep into the soil in search of moisture. Where moisture conditions 

 are suitable it will thrive on all kinds of soil. In California it grows 



[Cir. 59] 



