Walks: The Arboretum Trees History The original design for the University included plans for an arboretum that would serve as a 'zoo for trees'. Data was collected on exotic flora that could flourish in the Mediterranean climate of the Peninsula. Many eucalyptus were planted to serve as shade trees for the exotics between 1888 and Sen. Stanford's death in 1893. Upon Sen. Stanford's death, financial pressures disrupted arboretum development and the fast-growing eucalyptus flourished while most exotics died. Arboretum Eucalyptus c. 1940 Stanford University Archives Current Eucalyptus Die-off In 1990, the eucalyptus long-horned borer was inadvertently brought to San Diego and spread. Two decades later, 300 of the giant, 100-year old eucalyptus on campus had been killed. The eucalyptus are native of Australia where infestations are partially held in check by wasps that prey on the borer. In 1992, as the die-off continued, a plan was initiated to introduce the Australian wasps and to replace the now vulnerable eucalyptus with species native to the area. In 1998, the red gum lerp psyllid which both sucks nutrients from the eucalyptus and clogs gas-exchange pores needed for photosynthesis, was detected on campus. By 1999 it was found infesting more than 50 campus eucalyptus, leading to year-round rather than three-months-a-year leaf drop. In southern California where this invading species first appeared, trees are now beginning to die. Efforts to control the pest are underway. Future Plans By 2022 the Arboretum will have undergone a gradual transformation, as the eucalyptus-dominant woodland emerges into a woodland that emphasizes native species. Among these native species (California oaks, bays, buckeyes and maples) the remaining healthy eucalyptus and other exotics will be maintained. BACK