Читать книгу The Trees of San Francisco онлайн

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The blue gum is one of our largest trees: its towering crown can reach 150–200 feet in ideal conditions, and in its native Tasmania, the tree is known to reach 300 feet. The leaves of blue gums undergo an interesting change in shape as trees mature. The waxy juvenile leaves produced in the tree’s early years are silvery blue and rounded, occurring in opposite pairs on the branch. The deep green adult leaves are sickle shaped, thick, and leathery, and they hang vertically from the tree’s branches. This makes them perfectly adapted to the California coast’s dry but foggy summers. The leathery leaves retain moisture, and their vertical sickle shape causes the condensing fog to drip onto the ground, delivering moisture to the tree’s roots.

Blue gums are a major source of eucalyptus oil, which has disinfecting properties and is used in a number of products. The oil is extracted from the twigs and leaves of the tree. A row of mature blue gums on Octavia Street in Pacific Heights has an interesting San Francisco history; see “ssss1 and ssss1” on the previous page.