6 STATE HOARD OF FORESTRY. 



the genus have been manifested by nurserymen mid pioneer planters 

 ever since its introduction. More than 150 species have been identified 

 by botanists who have studied the Australian forests. Fully 100 of 

 these, including practically all the species eonsidered valuable for tim- 

 ber, have been introduced and planted in California. 



For general purposes, however, the blue gum has been used more 

 extensively than all other species combined, and even to-day the 

 knowledge of most laymen of the eucalypts is confined to their 

 acquaintance with this species. Several other species, however, possess 

 special qualities which warrant their selection for particular uses and 

 for certain localities. Among these are the sugar, manna, gray, red and 

 lemon gums, which, with the blue gum, owing to their rapid growth and 

 splendid development, rank as the timber eucalypts. 



SYLVICAL CHARACTERISTICS. 



Age and Size. In Australia the eucalypts reach ages of from 400 

 to 500 years, and dimensions second only to the California Sequoias. 

 Indeed, in height development, though not in diameter, they surpass 

 them. Many species are said to reach heights from 300 to over 400 

 feet, and diameters exceeding 12 to 15 feet. These dimensions result 

 from long periods of growth in the virgin forests, however, and no 

 such sizes have yet been attained by eucalypts planted in California. 



No eucalypt has grown to greater age than 40 years in this State. 

 At this age the period of rapid development has not been passed, and 

 no disposition to become short-lived is shown, as is frequently the 

 ease with species grown outside their habitat. Blue gum trees 175 

 feet in height and 5 or 6 feet in diameter have been produced here 

 in from twenty-four to thirty years. The single quality, rapidity of 

 growth, entitles the eucalypts to serious consideration, for no other 

 species can attain like dimensions in five times this period. 



Form. Naturally the timber eucalypts maintain an erect form, with 

 strong main axes and slender limbs. Young trees shoot up rapidly into 

 slender poles with scantily branched crowns and feathery, drooping 

 foliage. The bole gradually clears of limbs, particularly where the 

 density of the stand causes lateral shading. Open-grown timber has 

 more numerous and larger limbs. 



Tolerance. The timber eucalypts are species of moderate shade 

 endurance. During their early growth they will bear more shade than 

 later in life. The seedlings are even shade-demanding, and succeed 

 best under partial shade. When growth has commenced, however, full 

 lisrlit should be afforded them. 



