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RECOMMENDATIONS RE:CONTROL OF EUCALYPTUS IN LOS ALTOS HILLS 2 Large specimens of Tasmanian Blue Gum(Eucalyptus globulus)may be seen throughout the parts of California in which winter temperatures remain above 26`F. This species occurs naturally,however, only in the southeastern portion of Tasmania and in a few small areas on the southern coast of New South Wales on the mainland of Australia in areas of 1,000 foot elevation or less,with an average rainfall of 35"annually. In nature, it can reach 180 feet in height with a trunk diameter of 7 feet. Unfortunately,the higher nitrogen and phosphorous levels of the soils in many parts of the world where it has been planted, such as the Nilgire Hills of India,many parts of Portugal and California,have resulted in trees of 250'tall and 90' wide canopies. A specimen in the Alma Bridge Road area above Los Gatos reached a documented size of 130' in height and 30"trunk diameter in 35 years. This species has many characteristics which make it a nuisance or even dangerous when it is near human habitation. It re-seeds into almost any soil,and then grows so rapidly that it produces a dense canopy over-topping the native trees, shading them out. As Tasmanian Blue Gum specimens reach 2' or more in trunk diameter,they are voracious feeders, commonly using all available water and nutrients resulting in the common complaint that"nothing will grow under a Eucalyptus". By the time specimens reach this size,the thousands of seed pods, each containing hundreds of tiny black seeds produce so much viable seed that many seedlings appear within a hundred feet of the parent tree. By this means,a grove of Tasmanian Blue Gums can become the dominant species in a large area within a period of a few years,reaching 30-50' tall in 10 years. This species, like many other very large Eucalyptus species such as E. camaldulensis, E. viminalis, E. cladocalyx seem genetically predisposed to dropping 3-6"diameter, 15-20' long branches on a regular basis and an occasional 6-12"diameter limb which can weigh several hundred pounds. The unfortunate practice of over thinning the interior of trees by uninformed arborists when applied to large Eucalyptus species merely exacerbates the likelihood of limb drop by forming more and heavier end weight growth. The other unfortunate pruning procedure often used on large Eucalyptus is stub cutting in which whole tops of trees are removed down to 12"and 24"stubs. The trees response to this butchery is the production of water sprouts which often grow 10' per year,and are highly vulnerable to breaking off. PREPARED BY BARRIE D.COATE,CONSULTING ARBORIST MARCH 7TH,2006