The Tasmanian Blue Gum tree (Eucalyptus globulus) is not native to the Bay Area, but it has made itself at home here. Tilden Regional Park has acres of these menthol-fragranced giants, who have created their own environment of pale white columns reaching far upward before branching out into a haze of blue-green leaves. Woodpeckers go about their business in this unique habitat. The ground below is a bouncy yet ankle-swallowing, crackling carpet. A stiff breeze through the forest can produce banshee shrieks from resisting trunks. And as the sun sets and the native trees are already in shadow, the tops of “the Tasmanians” shine on in a silvery, glittering, eerie stratosphere of their own.